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Cook Strait
Cook Strait
Cook Strait
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Cook Strait (Māori: Te Moana-o-Raukawa, lit. 'The Sea of Raukawa') is a strait that separates the North and South Islands of New Zealand. The strait connects the Tasman Sea on the northwest with the South Pacific Ocean on the southeast. It is 22 kilometres (14 mi) wide at its narrowest point,[1] and has been described as "one of the most dangerous and unpredictable waters in the world".[2][3] Regular ferry services run across the strait between Picton in the Marlborough Sounds and Wellington.

Key Information

The strait is named after James Cook, the first European commander to sail through it, in 1770.[4] The waters of Cook Strait are dominated by strong tidal flows. The tidal flow through Cook Strait is unusual in that the tidal elevation at the ends of the strait are almost exactly out of phase with one another, so high water on one side meets low water on the other. A number of ships have been wrecked in Cook Strait with significant loss of life, such as the Maria in 1851,[5] the City of Dunedin in 1865,[6] the St Vincent in 1869,[5] the Lastingham in 1884,[7] SS Penguin in 1909[8] and TEV Wahine in 1968.

History

[edit]
See also: The legend of Whanganui-a-Tara

In Māori legend, Cook Strait was discovered by Kupe the navigator. Kupe followed in his canoe a monstrous octopus called Te Wheke-a-Muturangi across Cook Strait and destroyed it in Tory Channel or at Pātea.

When Dutch explorer Abel Tasman first saw New Zealand in 1642, he thought Cook Strait was a bight closed to the east. He named it Zeehaen's Bight, after the Zeehaen, one of the two ships in his expedition. In 1769 James Cook established that it was a strait, which formed a navigable waterway.[citation needed]

Cook Strait attracted European settlers in the early 19th century. Because of its use as a whale migration route, whalers established bases in the Marlborough Sounds, based out of Tory Channel and Port Underwood, and also in the Kāpiti area.[9][10][11] From the late 1820s until the mid-1960s Arapaoa Island was a base for whaling in the Sounds. Perano Head on the east coast of the island was the principal whaling station for the area from 1911.[12] The houses built by the Perano family are now operated as tourist accommodation.[13]

During the 1820s Te Rauparaha led a Māori migration to, and the conquest and settlement of, the Cook Strait region. In 1822 Ngāti Toa migrated to Cook Strait region, led by Te Rauparaha.[citation needed]

From 1840 more permanent settlements sprang up, first at Wellington, then at Nelson and at Whanganui (Petre). At this period the settlers saw Cook Strait in a broader sense than today's ferry-oriented New Zealanders: for them the strait stretched from Taranaki to Cape Campbell, so these early towns all clustered around "Cook Strait" (or "Cook's Strait", in the pre-Geographic Board usage of the times) as the central feature and central waterway of the new colony.

Pelorus Jack

Between 1888 and 1912 a Risso's dolphin named Pelorus Jack became famous for meeting and escorting ships around Cook Strait. Pelorus Jack was usually spotted in Admiralty Bay between Cape Francis and Collinet Point, near French Pass, a channel used by ships travelling between Wellington and Nelson. Pelorus Jack is also remembered after he was the subject of a failed assassination attempt. He was later protected by a 1904 New Zealand law.[14]

At times when New Zealand feared invasion, various coastal fortifications were constructed to defend Cook Strait. During the Second World War, two 23 cm (9.1 in) gun installations were constructed on Wrights Hill behind Wellington. These guns could range 28 kilometres (17 mi) across Cook Strait. In addition thirteen 15 cm (6 in) gun installations were constructed around Wellington, along the Mākara coast, and at entrances to the Marlborough Sounds. The remains of most of these fortifications can still be seen.

The Pencarrow Head Lighthouse at the entrance from Cook Strait to Wellington Harbour was the first permanent lighthouse built in New Zealand. Its first keeper, Mary Jane Bennett, was the only female lighthouse keeper in New Zealand's history. The light was decommissioned in 1935 when it was replaced by the Baring Head Lighthouse.

Geography

[edit]
View from Cape Koamaru of the Brothers Islands with Wellington west coast on the horizon

Approximately 18,000 years ago during the Last Glacial Maximum when sea levels were over 100 metres (330 feet) lower than present day levels, Cook Strait was a deep harbour of the Pacific Ocean, disconnected from the Tasman Sea by the vast coastal plains which formed at the South Taranaki Bight which connected the North and South islands. Sea levels began to rise 7,000 years ago, eventually separating the islands and linking Cook Strait to the Tasman Sea.[15]

The strait runs in a general NW-SE direction, with the South Island on the west side and North Island on the east. At its narrowest point, 22 kilometres (14 mi) separate Cape Terawhiti in the North Island from Perano Head on Arapaoa Island in the Marlborough Sounds.[1] Perano Head is actually further north than Cape Terawhiti. In good weather one can see clearly across the strait.

The west (South Island) coast runs 30 kilometres (19 mi) along Cloudy Bay and past the islands and entrances to the Marlborough Sounds. The east (North Island) coast runs 40 kilometres (25 mi) along Palliser Bay, crosses the entrance to Wellington Harbour, past some Wellington suburbs and continues another 15 kilometres (9.3 mi) to Mākara Beach.

The Brothers is a group of tiny islands in Cook Strait off the east coast of Arapaoa Island. North Brother island in this small chain is a sanctuary for the rare Brothers Island tuatara, while the largest of the islands is the site of the Brothers Island Lighthouse.

Wellington's coast, seen from Cook Strait

The shores of Cook Strait on both sides are mostly composed of steep cliffs. The beaches of Cloudy Bay, Clifford Bay, and Palliser Bay shoal gently down to 140 metres (460 ft), where there is a more or less extensive submarine plateau. The rest of the bottom topography is complex. To the east is the Cook Strait Canyon with steep walls descending eastwards into the bathyal depths of the Hikurangi Trough. To the north-west lies the Narrows Basin, where water is 300 and 400 metres (980 and 1,310 ft) deep. Fisherman's Rock in the north end of the Narrows Basin rises to within a few metres of low tide, and is marked by waves breaking in rough weather. A relatively shallow submarine valley lies across the northern end of the Marlborough Sounds. The bottom topography is particularly irregular around the coast of the South Island where the presence of islands, underwater rocks, and the entrances to the sounds, create violent eddies.[1] The strait has an average depth of 128 metres (420 ft).[citation needed]

In 1855 a severe earthquake occurred on both sides of Cook Strait.[citation needed] In 2013 two large earthquakes measuring 6.5 and 6.6 on the Richter Scale struck Cook Strait, causing significant damage in the town of Seddon, with minor to moderate damage in Wellington.[citation needed]

Oceanography

[edit]
External images
image icon Animation of the tides in Cook Strait – NIWA
image icon Animation of the lunar (M2) tide component around NZ
image icon Cook Strait currents before and after high tide at Wellington – Te Ara: The Encyclopedia of New Zealand
image icon Underwater topography of Cook Strait – National Library of New Zealand
See also: Cook Strait tides

The waters of Cook Strait are dominated by strong tidal flows. The tidal flow through Cook Strait is unusual in that the tidal elevation at the ends of the strait are almost exactly out of phase with one another, so high water on one side meets low water on the other.[16] This is because the main M2 lunar tide component that happens about twice per day (actually 12.42 hours)[17] circulates anti-clockwise around New Zealand, and is out of phase at each end of the strait (see animation on the right). On the Pacific Ocean side the high tide occurs five hours before it occurs at the Tasman Sea side. On one side is high tide and on the other is low tide. The difference in sea level can drive tidal currents up to 2.5 metres per second (5 knots) across Cook Strait.[18][19]

There are numerous computer models of the tidal flow through Cook Strait. While the tidal components are readily realisable,[20] the residual flow is more difficult to model.[21] Probably the most prolific oceanographer to research the strait was Ron Heath based at the N.Z. Oceanographic Institute. He produced a number of studies including analysis of tides [22] which identified the presence of a "virtual amphidrome" in the region. Heath also quantified a best estimate for the time of the "residual current" (i.e. net current after averaging out the tidal influence) in the strait.[23] This continues to be a topic of research with computer simulations combining with large datasets to refine the estimate.[24]

Historical ocean sampling locations within Cook Strait
Global surface elevation of the M2 ocean tide (NASA).[17] This computer animation shows the peaks and troughs of the M2 tides sweeping anticlockwise around New Zealand. When it is high tide on one side of Cook Strait, it is low tide on the other side. For this reason, the strait can experience exceptionally fast tidal flows.

Despite the strong currents, there is almost zero tidal height change in the centre of the strait. Instead of the tidal surge flowing in one direction for six hours and then in the reverse direction for six hours, a particular surge might last eight or ten hours with the reverse surge enfeebled. In especially boisterous weather conditions the reverse surge can be negated, and the flow can remain in the same direction through three surge periods and longer. This is indicated on marine charts for the region.[25] Furthermore, the submarine ridges running off from the coast complicate the ocean flow and turbulence.[26] The substantial levels of turbulence have been compared to that observed in the Straits of Gibraltar and Seymour Narrows in British Columbia.[27]

Marine life

[edit]

Cook Strait is an important habitat for many cetacean species. Several dolphins (bottlenose, common, dusky) frequent the area along with killer whales and the endemic Hector's dolphins. Long-finned pilot whales often strand en masse at Golden Bay. The famous Pelorus Jack was a Risso's dolphin being observed escorting the ships between 1888 and 1912, though this species is not a common visitor to the New Zealand's waters. Large migratory whales attracted many whalers to the area in the winter. Currently, an annual survey of counting humpback whales is taken by Department of Conservation and former whalers help DOC to spot animals by using several vantage points along the strait such as on Stephens Island. Other occasional visitors include southern right whales, blue whales, sei whales and sperm whales. Giant squid specimens have been washed ashore around Cook Strait or found in the stomachs of sperm whales off Kaikōura.

A colony of male fur seals has long been established near Pariwhero / Red Rocks on the south Wellington coast.[28] Cook Strait offers good game fishing. Albacore tuna can be caught from January to May. Broadbill swordfish, bluenose, mako sharks and the occasional marlin and white shark can also be caught.[29]

Transport

[edit]
External videos
video icon Ship entering a Cook Strait swell
– YouTube
Cook Strait ferries in Wellington Harbour

Ferry services

[edit]
See also: Transport in New Zealand § Ferry services, and Marlborough Sounds § Ferries and marine farms

Regular ferry services run between Picton in the Marlborough Sounds and Wellington, operated by KiwiRail (the Interislander) and StraitNZ (Bluebridge). Both companies run services multiple times a day. Roughly two thirds of the crossing is in the strait, and the remainder mainly within the Sounds. The journey covers 93 kilometres (58 mi) and takes about three and a half hours. The strait often experiences rough water and heavy swells from strong winds, especially from the south. New Zealand's position directly athwart the roaring forties means that the strait funnels westerly winds and deflects them into northerlies. As a result, ferry sailings are often disrupted and Cook Strait is regarded as one of the most dangerous and unpredictable waters in the world.[citation needed] In 1962 the first ferry service to allow railway carriages, cars and trucks began with GMV Aramoana.[30] In 1994 the first fast-ferry service began operation across Cook Strait.[citation needed]

Shipwrecks and major events

[edit]
See also: Category:Shipwrecks of the Cook Strait

In 1851 the barque Maria wrecked on rocks at Cape Terawhiti, killing 26 people.[31] In 1865 the paddle steamer City of Dunedin sank, killing 50 to 60 people.[32] In 1869 St Vincent wrecked in Palliser Bay, killing 20 people.[33] In 1884 Lastingham was wrecked in a gale at Cape Jackson, killing 18 people[34][35][36] and carrying rails for the Wellington & Manawatu Railway, which were salvaged.[37] In 1909 SS Penguin wrecked in Cook Strait, killing 75 people.[8] In 1968, the TEV Wahine, a Wellington–Lyttelton ferry of the Union Company, foundered at the entrance to Wellington Harbour and capsized. Of the 610 passengers and 123 crew on board, 53 died.[38] On 16 February 1986 the cruise ship Mikhail Lermontov struck rocks at Cape Jackson at the northern tip of the Marlborough Sounds and sank in Port Gore, with one person killed.[39]

In 2006, 14-metre (46 ft) waves resulted in the Interislander ferry DEV Aratere slewing violently and heeling to 50 degrees, the sailing took 7 hours. Three passengers and a crew member were injured, five rail wagons were toppled and many trucks and cars were heavily damaged. The journey is often regarded as one of the worst trips across the strait. Maritime NZ's expert witness Gordon Wood claimed that if the ferry had capsized most passengers and crew would have been trapped inside and would have had no warning or time to put on lifejackets.[40][41]

In 1990 Stephen Preest made the first crossing and double crossing by hovercraft.[42]

In 2005, the retired frigate HMNZS Wellington was sunk in Cook Strait off the south coast of Wellington as an artificial reef.[43]

Air services

[edit]
Further information: List of Cook Strait crossings by air

The first aeroplane flight across Cook Strait occurred in 1920,[44] jet aeroplane in 1946,[citation needed] helicopter crossing in 1956,[45] glider crossing in 1957,[46] balloon crossing (by Roland Parsons and Rex Brereton) in 1975,[47] microlight aircraft in 1982,[45] autogyros in 1999,[48] paraglider (by Matt Standford) in 2013.[49] In 2021 the first electric aircraft flight across Cook Strait, from Omaka Aerodrome to Wellington Airport, by Gary Freedman in a Pipistrel Alpha Electro.[50][51]

Air services began across Cook Strait in 1935.[citation needed] Air lines which operate or have operated flights across Cook Strait include Air New Zealand, Originair, Straits Air Freight Express, Air2there, CityJet and Sounds Air.[citation needed]

Proposals for a bridge or tunnel

[edit]

Proposals have been made for a bridge or tunnel across Cook Strait.[52][53][54][55][56][57] As of January 2025, a tunnel is estimated to cost NZ$50 billion, equivalent to 20 years of New Zealand's transport infrastructure development budget. Other obstacles include the large amount of seismic activity in Cook Strait.[57]

Cables

[edit]
See also: HVDC Inter-Island

In 1866, the first telegraph cable was laid in Cook Strait from Lyall Bay on Wellington’s south coast to Whites Bay, north of Blenheim, connecting the South Island telegraph system to Wellington.[58][59] In 1879 the vessel Kangaroo laid a further 120-nautical-mile-long (220 km) telegraph cable across Cook Strait from Whanganui to Wakapuaka, near Nelson.[60]

In 1964, three submarine power cables were installed across Cook Strait between Oteranga Bay in the North Island and Fighting Bay in the South Island as part of the HVDC Inter-Island link, to enable transmission of electricity between Benmore in the South island and Haywards in the North Island.[61][62][63]

In 1991 three new power and two communication cables were laid to replace the original cables. Each of the replacement HVDC power cable operates at 350 kV, and can carry up to 500 MW, with Pole 2 of the link using one cable and Pole 3 using two cables. The link's total capacity was increased to 1200 MW (500 MW for Pole 2 and 700 MW for Pole 3). The cables are laid on the seabed within a legally defined zone called the cable protection zone (CPZ). The CPZ is about 7 kilometres (4 mi) wide for most of its length, narrowing where it nears the terminals on each shore. Fishing activities and anchoring boats are prohibited within the CPZ.[64] From 1994, the HVDC link across Cook Strait has been operated by Transpower.

Fibre optic cables carry telecommunications across Cook Strait, used by New Zealand's main telecommunication companies for domestic and commercial traffic and by Transpower for control of the HVDC link. In 2002 two further communications cables were laid.[citation needed]

In May 2025, Transpower announced that it was planning for replacement of all three existing Cook Strait HVDC cables laid in 1991. The forecast cost of replacement was $NZD 1.4 billion and the project was scheduled for completion by 2031. The replacement plan included adding a fourth cable to increase inter-island transmission capacity and resilience, together with enhancements to the cable terminal stations on either side of Cook Strait.[65]

Tidal power

[edit]
See also: Ocean power in New Zealand

Cook Strait has been identified as a potentially excellent source of tidal energy.[66]

In April 2008, Neptune Power was granted a resource consent to install a $10 million experimental underwater tidal stream turbine capable of producing one megawatt. The turbine was designed in Britain, and was to be built in New Zealand and placed in 80 metres (260 ft) of water, 4.5 kilometres (2.8 mi) due south of Sinclair Head, in waters known as the "Karori rip". The company claimed there is enough tidal movement in Cook Strait to generate 12 GW of power, more than one-and-a-half times New Zealand's current requirements.[67][68][69][19] In practice, only some of this energy could be harnessed.[70] As of October 2016, this turbine had not been built and the Neptune Power website is a placeholder with no further announcements.

On the other side of the strait, Energy Pacifica applied for resource consent to install up to 10 marine turbines, each able to produce up to 1.2 MW, near the Cook Strait entrance to Tory Channel. The company claimed that Tory Channel was an optimal site with a tidal current speed of 3.6 metres per second (12 ft/s) and the best combination of bathymetry and accessibility to the electricity network.[19] However, despite being validated by computer modelling,[71] no project was forthcoming.

Swimming

[edit]
Track of a swimmer's path crossing Cook Strait in 1972

According to oral tradition, the first woman to swim Cook Strait was Hine Poupou. She swam from Kapiti Island to d'Urville Island with the help of a dolphin.[72] Other Māori accounts tell of at least one swimmer who crossed the strait in 1831. In modern times, the strait was swum by Barrie Devenport in 1962. Lynne Cox was the first woman to swim it, in 1975.[73] The most prolific swimmer of the strait is Philip Rush, who has crossed eight times, including two double crossings. Aditya Raut was the youngest swimmer at 11 years. Caitlin O'Reilly was the youngest female swimmer and youngest New Zealander at 12 years. Pam Dickson was the oldest swimmer at 55 years.[74] John Coutts was the first person to swim the strait in both directions.[75] By 2010, 74 single crossings had been made by 65 individuals, and three double crossings had been made by two individuals (Philip Rush and Meda McKenzie). In March 2016, Marilyn Korzekwa became the first Canadian and oldest woman, at 58 years old, to swim the strait.[76]

Crossing times by swimmers are largely determined by the strong and sometimes unpredictable currents that operate in the strait.[74] In 1980 the oceanographer Ron Heath published an analysis of currents in Cook Strait using the tracks of swimmers. This was from a time when detailed measurement of ocean currents was technologically difficult.[77]

In 1984 Philip Rush swam the strait both ways.[78] In 1984 Meda McKenzie became the first woman to swim the strait both ways.[79]

See also

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References

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Sources cited

[edit]
  • Grady, Don (September 1982). Perano Whalers of Cook Strait, 1911–1964. Intl Specialized Book Service. p. 238. ISBN 978-0-589-01392-9.
  • Harris, Thomas Frank Wyndham (1990). Greater Cook Strait. DSIR Marine and Freshwater. p. 212. ISBN 0-477-02580-3.
  • Young, Victor (2009). Strait Crossing: The ferries of Cook Strait through time. Wellington, NZ: Transpress NZ. ISBN 9781877418112.
[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Cook Strait

View on Grokipedia
from Grokipedia
Cook Strait (Māori: Te Moana-o-Raukawa) is a strait separating New Zealand's from the , connecting the to the west with the South Pacific Ocean to the east. It measures 22 kilometres at its narrowest point between Cape Terawhiti on the and Perano Head on Arapaoa Island, with an average depth of 128 metres, though depths exceed 300 metres in the central Narrows Basin and plunge to over 2,500 metres in associated submarine canyons. The strait spans approximately 40 kilometres in length and lies within the wind belt, resulting in frequent strong westerly winds and tidal currents reaching speeds of 1.5–2 metres per second, creating turbulent conditions notorious for challenging navigation. Named after Captain , who first navigated the strait in 1770 during his exploration of New Zealand's coasts, it holds significant cultural importance to as a traditional pathway for migration, trade, and resource gathering. Geologically, Cook Strait is shaped by active along the boundary of the Pacific and Australian plates, featuring fault lines such as the Marlborough Fault System and a complex submarine canyon network that incises the seafloor, facilitating and marine . The region's dynamic environment supports diverse ecosystems, including habitats for marine mammals like whales and dolphins, while its position makes it a critical corridor for commercial shipping and inter-island ferry services between Wellington and Picton, carrying over one million passengers and hundreds of thousands of vehicles annually. Despite its importance, Cook Strait's hazardous conditions—exacerbated by unpredictable weather, steep waves, and strong rips—have led to numerous maritime incidents, prompting specialized endorsements for and ongoing into tidal energy potential. The strait also attracts adventurers, notably open-water swimmers who attempt its 22-kilometre crossing, a feat first achieved in 1962 and now governed by strict protocols due to the risks involved.

History and Cultural Significance

Māori Perspectives and Legends

In Māori tradition, Cook Strait is known as Te Moana-o-Raukawa (Raukawa or Raukawa Moana), referring to the "sea of Raukawa," a name derived from a native with fragrant leaves that grows along its shores. This waterway holds profound cultural and spiritual significance as a sacred passage central to ancestral narratives, facilitating trade, migration routes between the North and South Islands, and spiritual connections to the sea god . A pivotal recounts the discovery of the by the navigator around the 10th century, during his voyage from aboard the waka Matahourua. Pursuing the giant octopus , which had been stealing fish from his lines, Kupe chased the creature across the ocean, culminating in a fierce battle in the waters of Raukawa Moana near Tory Channel, where he slew it with a whalebone . This epic pursuit not only established the strait as a key navigational pathway in Polynesian voyaging but also embedded it in oral histories as a place of heroic deeds and separation of the islands, with landmarks like Te Whekenui Bay commemorating the event. Traditional travel across Raukawa Moana involved waka voyages for inter-tribal connections, fishing, and resource gathering, as preserved in oral histories that describe crossings for kai moana () such as shellfish and , essential for sustenance and . These journeys, often undertaken in double-hulled waka equipped with sails and navigated by stars, currents, and landmarks, fostered alliances and exchanges between on either side of the strait, despite its treacherous tides. The strait plays a vital role in iwi identities, particularly for Ngāti Kuia and Rangitāne, descendants of the Kurahaupō waka that arrived in the region around the , establishing territories in areas like Pelorus Sound and Wairau. For these , Raukawa Moana serves as both a natural boundary defining traditional (tribal areas) and a meeting place for cultural and resource-based interactions, reinforcing (genealogy) tied to its waters.

European Exploration and Naming

The first European contact with the region of Cook Strait occurred during the voyage of Dutch explorer in December 1642. Tasman, commanding the ships Heemskerck and Zeehaen, sailed northward along the west coast of what is now New Zealand's after anchoring in Golden Bay (then named Murderers' Bay following a fatal encounter with ). Strong tidal currents indicated an opening to the east, but persistent poor visibility and adverse weather led him to misidentify the feature as a large bay rather than a , which he charted as Zeehaen's Bight on his map Nova Zeelandia. Nearly 128 years later, British navigator definitively identified and transited the strait during his first Pacific voyage aboard HMS Endeavour. In late January 1770, after anchoring in Ship Cove within Queen Charlotte Sound on the , Cook led an expedition to a nearby hill (now known as Cooks Lookout on Arapawa Island), from where he observed the narrow passage connecting the to the and separating New Zealand's two principal islands. He then sailed through the strait from south to north between 15 and 20 February 1770, producing detailed charts that accurately depicted its turbulent currents and intervening islands such as Kapiti. Although Cook did not explicitly name the strait after himself in his journal, it became known as Cook Strait in recognition of his exploration, likely through the influence of expedition botanist . Subsequent European voyages further validated Cook's findings. In November 1791, British explorer , on his North Pacific expedition aboard HMS Discovery, anchored in Dusky Sound on the South Island's southwest coast before navigating northward through the strait, confirming its role as the key waterway dividing the North and South Islands amid challenging winds and currents. Vancouver's observations reinforced the strait's strategic importance for maritime passage between the islands. In the early , systematic hydrographic surveys by British naval officers refined the mapping of Cook Strait, addressing navigational hazards for increasing colonial traffic. Officers from vessels such as HMS Alligator and later survey ships measured key dimensions, determining the minimum width at approximately 22 kilometers between Cape Terawhiti on the and Perano Head on Arapaoa Island, while documenting depths averaging 128 meters and peak tidal flows exceeding 4 knots. These efforts, building on Cook's foundational charts, established the strait as a vital but perilous corridor for shipping.

Historical Settlements and Events

In the early , European activities flourished around Cook Strait, with shore-based stations established on both the North and coasts to exploit the migratory southern right whales passing through the area. One of the earliest stations was set up around 1827 at Te Awaiti on Arapawa Island in the by John Guard, marking the beginning of organized operations that attracted and employed laborers from local such as Ngāti Koata and Rangitāne. By the 1830s, additional stations dotted the strait’s shores, including sites at Cloudy Bay and Port Underwood, where integrated crews of whalers and workers processed and bone, fostering early intercultural exchanges but also introducing muskets that altered traditional power dynamics. During the 1820s, Ngāti Toa leader Te Rauparaha orchestrated migrations and raids across Cook Strait, utilizing large waka taua to expand his people’s influence from Kāwhia to the Kapiti Coast and beyond. In approximately 1827, Te Rauparaha led an initial war party across the strait to the Wairau region, capturing several Rangitāne pā and securing a foothold on the South Island, followed by larger invasions that displaced or allied with local tribes. These crossings were pivotal in the Musket Wars (c. 1807–1842), a series of intertribal conflicts exacerbated by the introduction of firearms through trade with Europeans, resulting in significant population displacements and conquests around the strait, including the subjugation of Ngāti Apa and Rangitāne territories. European colonization intensified in the 1840s, with the New Zealand Company establishing Wellington as a major port on the strait’s northern shore in January 1840, drawing hundreds of settlers amid ambitious land acquisition plans. The signing of the Treaty of Waitangi on February 6, 1840, between the British Crown and over 500 Māori rangatira promised protection of Māori land rights while granting the Crown pre-emptive purchase authority, yet it sparked disputes in Cook Strait regions as the Company’s prior sales of land in Wellington and Nelson conflicted with Māori ownership claims. These tensions culminated in events like the 1843 Wairau Affray near the strait, where settlers clashed with Ngāti Toa over contested land, highlighting the treaty’s uneven implementation and leading to prolonged legal and armed conflicts over iwi territories on both shores. Meanwhile, the first organized European settlers arrived in Nelson on February 1, 1842, via the ship Fifeshire, establishing a planned community that relied on the strait for trade and communication, though early years were marked by land shortages and Māori-settler negotiations. A notable natural phenomenon during this era was , a Risso’s first observed in 1888 guiding ships through the hazardous French Pass channel in the at the strait’s southeastern entrance. For over two decades until around 1912, Jack routinely escorted vessels, particularly those of the Union Steam Ship Company, from Pelorus Sound to the open strait, earning fame and legal protection under a 1904 that made him ’s first individually safeguarded after an attempted shooting. His presence symbolized the strait’s perilous navigation and became a for mariners and settlers. As global tensions escalated, prompted the construction of coastal fortifications along Cook Strait’s shores to defend against potential naval threats, with batteries installed at strategic sites like Fort Ballance near and gun emplacements on Blumine Island in the . From 1940 onward, these defenses included searchlights, anti-aircraft guns, and radar stations manned by and Allied forces, reflecting fears of Japanese incursions following the 1941 attack, though no major engagements occurred in the strait. By 1945, over a dozen such sites ringed the waterway, underscoring its role as a vital southern gateway to ’s key ports.

Geography and Geology

Location and Physical Features

Cook Strait lies between New Zealand's and , specifically separating the Kapiti Coast and to the north from the and Cloudy Bay area to the south. It serves as a critical connecting the on its northwestern side to the South Pacific Ocean on its southeastern side. The strait spans approximately 40 km in an east-west orientation, encompassing surrounding coastal features such as Palliser Bay on the 's southeast flank and Tasman Bay adjacent to the 's northwest. At its narrowest point, between Cape Terawhiti on the and Perano Head on Arapaoa Island in the , the strait measures 22 km across, providing the shortest sea passage between the two main islands. The coastal topography is characterized by steep cliffs rising sharply from the water on both sides, interspersed with bays and inlets that add complexity to the shoreline. On the southern side, the form a intricate network of drowned river valleys, created through tectonic that submerged ancient fluvial systems, resulting in a labyrinth of channels, islands, and sheltered waterways. Several notable islands punctuate the strait, including The Brothers—a group comprising North Brother and South Brother islets—located off the northeastern tip of Arapaoa Island, as well as Entry Island (also known as ) near the northern entrance. These islands, particularly The Brothers and Kapiti, function as protected bird sanctuaries, hosting diverse populations and supporting conservation efforts for native . The overall landscape reflects the broader tectonic activity that has shaped the region, with the strait's formation linked to the submergence of a prehistoric due to ongoing plate boundary movements.

Geological Formation and Seismicity

Cook Strait's modern configuration resulted from post-Ice Age approximately 7,000 years ago, which submerged a river valley connecting the North and South Islands of . During the around 20,000 years ago, global sea levels were about 120 meters lower than present, exposing the continental shelf and forming a across what is now the strait. As glaciers melted, rising seas progressively inundated the valley, with initial breaching occurring around 15,000–16,000 years , though the current bathymetric profile stabilized with the sea level rise culminating near 7,000 years ago. The strait has an average depth of 128 meters and reaches a maximum depth exceeding 300 meters, contributing to its dynamic tidal regime. A prominent feature is the Cook Strait Canyon, a large, multi-branched mega-canyon system extending southward from the strait's eastern margin into the Hikurangi zone; this shelf-incising structure spans about 1,800 square kilometers and reaches depths of up to 2,700 meters, shaped by both erosional processes and ongoing tectonic activity. The canyon's development reflects the interplay of post-glacial and tectonic deformation along New Zealand's active margin. Geologically, Cook Strait lies at the transition of New Zealand's plate boundary, where the Pacific Plate subducts obliquely beneath Plate at a rate of about 42 millimeters per year, transitioning from in the south to in the north. This position places the strait within the highly active Marlborough Fault System, a network of dextral strike-slip faults including the Fault, which accommodates much of the plate motion through the region. The area's is elevated due to this tectonic setting, with frequent earthquakes resulting from fault slip and associated crustal deformation. Significant seismic events in Cook Strait's history include the , a magnitude 8.2 event centered near the Fault that caused widespread uplift and around the strait, along with a reaching heights of up to 10–11 meters in parts of Cook Strait. More recently, the 2013 Seddon (magnitude 6.5) and the subsequent Lake Grassmere (magnitude 6.6), both nucleating in the Cook Strait region, generated minor with waves up to 1 meter high and minor damage to infrastructure. In 2023, a magnitude 6.3 struck the Cook Strait region, causing strong shaking felt across central but no significant or major damage. These events underscore the strait's vulnerability to moderate-to-large , which can propagate across its narrow confines and impact surrounding coastal areas.

Oceanography and Climate

Tidal and Current Dynamics

The tides in Cook Strait are predominantly semidiurnal, dominated by the M₂ constituent, with typical spring tidal ranges of 1 to 1.5 meters along the strait. This pattern arises from the broader amphidromic system encircling New Zealand's coastline, where the tidal wave propagates counterclockwise around the islands, resulting in significant phase variations across the region. In Cook Strait specifically, the M₂ tidal phase differs by approximately 150 degrees (equivalent to about five hours) between the western entrance near Tasman Bay and the eastern exit toward the , creating a near-standing wave configuration that drives bidirectional tidal flows. This phase lag amplifies water movement within the narrow channel, generating peak tidal currents of up to 3.4 meters per second (about 6.6 knots) during spring tides, particularly in constricted areas like the Karori Rip near Cape Terawhiti. The strong flows are further influenced by residual circulation from the South Taranaki Bight, where a counterclockwise gyre contributes to enhanced velocities as water enters the strait via the d'Urville Current. Near Cape Terawhiti, the combination of tidal amplification and topography produces complex turbulent features, including eddies and steep standing waves in the rip, which can reach speeds of 2 to 3 meters per second under typical conditions. Oceanographic studies, including those by Ron Heath in the late 1970s and subsequent NIWA modeling efforts, have elucidated these dynamics through data and numerical simulations. Heath's analysis of tidal constituents highlighted the semidiurnal dominance and phase-driven rectification leading to residual east-west flows of 0.1 to 0.2 per second. NIWA's high-resolution models reveal persistent eddies along the strait's flanks and localized zones, especially during ebb , where vertical mixing reaches depths of 50 and supports entrainment from the seafloor. These features contribute to the strait's overall volume flux, with the M₂ tidal component alone accounting for an amplitude of 4.68 Sverdrups.

Climate Influences and Environmental Changes

Cook Strait experiences predominant westerly winds, which are channeled through the narrow passage between the North and South Islands of , often intensifying due to topographic effects. These frequently interact with the to form barrier jets, leading to strong southerly winds in the region, particularly during frontal passages. Average wind speeds in the strait typically range from 15 to 20 knots, with gusts reaching up to 50 knots during intense events, contributing to challenging conditions. Climate change is exerting significant influences on Cook Strait's marine environment, with sea surface temperatures rising by approximately 1°C since 1900, driven by global ocean warming trends. This warming has led to more frequent and intense marine heatwaves, particularly in the northern Cook Strait, where persistent warm water anomalies have been observed in recent years. In 2023 and , New Zealand experienced record-high sea surface temperatures, exacerbating marine heatwaves in the region. Additionally, increased intensity associated with a warming atmosphere has amplified wave heights, heightening risks of along the strait’s margins, such as in the and Wellington region. Ocean acidification, resulting from elevated atmospheric CO2 absorption, has caused a pH drop of about 0.1 units in New Zealand's coastal waters since pre-industrial times, affecting the strait’s chemistry. Sea level rise, observed at around 2.2 mm per year in the Wellington area since the early 1900s, is projected to reach 0.3 to 1 meter by 2100, potentially amplifying tidal ranges and exacerbating inundation risks in low-lying coastal areas. Long-term monitoring at the Baring Head atmospheric station, operational since 1972, provides critical data on rising CO2 levels—now averaging over 423 ppm annually (as of 2024)—serving as a key proxy for regional climate trends and greenhouse gas influences on the strait.

Marine Ecology

Biodiversity and Key Species

Cook Strait hosts a rich array of marine , particularly among cetaceans, which utilize the strait as a critical migration corridor and foraging habitat due to its position between the North and South Islands. Hector's dolphins (Cephalorhynchus hectori), an endangered , maintain a distinct subpopulation of approximately 230 individuals (as of 2017) in the Cloudy/Clifford Bay area adjacent to the strait, with smaller groups in nearby sounds, where they inhabit shallow coastal waters for feeding and calving. Southern right whales (Eubalaena australis), classified as vulnerable, regularly pass through the region during their seasonal migrations between feeding grounds and subtropical breeding areas, as evidenced by historical records and modern satellite tracking data. pods (Orcinus orca) are frequently observed in the strait, often in family groups hunting and other marine mammals in the dynamic waters. Sperm whales (Physeter macrocephalus), also vulnerable, exploit the deep eastern portions of Cook Strait for feeding on deep-sea prey, with acoustic monitoring confirming their presence year-round and along migration routes. Seabirds and pinnipeds contribute significantly to the strait's ecological diversity, with species adapted to the nutrient-rich upwellings and island habitats. New Zealand fur seals (Arctocephalus forsteri) form breeding colonies at sites like Cape Palliser and Ward Beach–Needles Point along the strait's margins, hauling out on rocky shores and islands for resting and pup-rearing, while foraging extensively in surrounding waters for fish and squid. Little blue penguins (Eudyptula minor), the world's smallest penguin species, nest in coastal burrows and rocky crevices around the strait, particularly in sheltered bays, where they dive for small fish and squid during nocturnal foraging trips. Several albatross species frequent Cook Strait's surface waters, including the white-capped albatross (Thalassarche steadi), which scavenges near fishing vessels, the black-browed albatross (Thalassarche melanophris), often seen offshore, and wandering albatross (Diomedea exulans), which glide over deeper channels; these seabirds benefit from the strait's productivity but face incidental interactions with fisheries. Fish populations in Cook Strait reflect its role as a transitional zone between subtropical and waters, supporting both game and commercial species. Hoki (Macruronus novaezelandiae), a key deepwater fish, spawns in the strait from late June to mid-September, drawing large seasonal aggregations that form the basis of New Zealand's largest commercial , with peak activity in and . Kahawai (), a schooling predator, inhabits the 's northern reaches up to 150 meters depth, preying on smaller fish and crustaceans while serving as a popular recreational target. Snapper (Chrysophrys auratus) occupy shallower rocky reefs and sandy bottoms around the strait, particularly in coastal embayments, where they graze on shellfish and crustaceans. Albacore tuna (Thunnus alalunga), a migratory pelagic species, transits through the region during warmer months, pursued by both commercial longliners and sport fishers for its high-speed surface runs. Invertebrate communities thrive in Cook Strait's subtidal habitats, with forests acting as hotspots that shelter diverse assemblages. Paua (Haliotis iris), an iconic , clings to rocky substrates in the strait's intertidal and subtidal zones, grazing on and supporting both customary and commercial harvests, with enhancement efforts like seeding juvenile stock south of Tory Channel to bolster populations. (Architeuthis dux), elusive deep-sea cephalopods, inhabit the strait's offshore depths, occasionally washing ashore on beaches as evidenced by historical strandings between 1879 and 1887, and serving as primary prey for sperm whales. Dense forests, dominated by Ecklonia radiata, extend across rocky reefs and provide three-dimensional structure for over 180 associated fish and invertebrate species, including sponges, , crabs, and sea urchins (kina), fostering high productivity amid the strait's strong currents that influence .

Conservation Efforts and Threats

Cook Strait's marine environment benefits from several adjacent protected areas designed to preserve biodiversity and mitigate human impacts. The Kapiti Marine Reserve, established in 1992, encompasses 2,167 hectares around Kapiti Island and the surrounding seabed, prohibiting fishing and extraction to safeguard habitats for fish, seals, and dolphins. Similarly, the Clifford and Cloudy Bay Marine Mammal Sanctuary, designated in 2008, covers coastal waters south of the strait to protect endangered Hector's dolphins from activities like seismic surveying and seabed mining. These areas contribute to broader ecosystem resilience by restricting commercial pressures in key foraging and breeding zones. Human-induced threats significantly challenge the strait's ecological integrity. , particularly in the hoki trawl , has led to notable mortality of fur seals, with estimates indicating 100–250 affected annually in Cook Strait waters (2012–2021 mean: 124). disperses rapidly via the strait's strong currents, as demonstrated by oceanographic models simulating debris trajectories from coastal drop points, exacerbating ingestion risks for marine species like dolphins. Vessel strikes pose a direct hazard to marine mammals in this busy shipping corridor, where high and commercial traffic increases collision probabilities for migratory whales and resident dolphins. Additionally, habitat loss from , driven by land runoff in adjacent , smothers benthic communities and reduces suitable areas for key species. Conservation initiatives involve collaborative monitoring and protection strategies. The National Institute of Water and Atmospheric Research (NIWA) deploys acoustic moorings to track cetacean distributions and vocalizations in Cook Strait, aiding in the identification of high-use areas for species like blue whales and beaked whales. The Department of Conservation (DOC) focuses on seal protection through bycatch mitigation in fisheries and population assessments, emphasizing reduced incidental captures in the hoki fishery. On an international level, the and Cook Strait Important Area (IMMA), recognized in 2018, promotes global standards for and habitat conservation by highlighting threats and advocating for reduced disturbances. Recent concerns center on from ship hulls and introductions via ballast water, given the strait's role as a shipping route; these vectors have facilitated non-native species establishment in waters, potentially altering local food webs. Efforts to address these include national protocols under the Ministry for Primary Industries, which enforce ballast water management to minimize risks in high-traffic zones like Cook Strait.

Transportation

Ferry Services

Commercial ferry services across Cook Strait primarily operate between on the and Picton on the , providing essential connectivity for passengers, vehicles, and freight. The two main operators are , managed by , and Bluebridge, operated by , which together facilitate the majority of crossings. These services are critical to New Zealand's economy, transporting approximately 1 million passengers and over 5 million tonnes of freight annually, including both road and rail that supports national supply chains. Interislander and Bluebridge each offer 3 to 5 sailings daily in each direction, with typical journey durations of about 3.5 hours, depending on weather conditions. The ferries accommodate cars, trucks, and passengers, with vessels also handling rail wagons to enable seamless inter-island rail freight movement. In 2024 and 2025, services achieved high reliability during summer peak periods, with minimal disruptions reported, though weather-related cancellations occurred around 150 times over the year, averaging three per week, primarily due to strong winds and swells in the strait. A significant fleet development in 2025 was the retirement of Interislander’s rail-enabled ferry Aratere on August 18, following 26 years of service, to allow for port infrastructure upgrades in Picton. This vessel, which had carried passengers and freight since 1999, was sold for recycling in India. To modernize operations, KiwiRail has contracted Guangzhou Shipyard International in China to build two new 200-meter rail-enabled ferries, capable of accommodating 1,500 passengers each, scheduled to enter service in 2029 as part of a broader replacement project estimated at NZ$1.4 billion, including vessel construction and terminal enhancements. These new vessels will feature hybrid electric propulsion systems for reduced emissions, building on earlier electrification initiatives announced for the fleet.

Aviation and Other Modes

The first powered flight across Cook Strait occurred on 25 August 1920, when Captain Euan Dickson piloted an Avro 504K biplane from to (near ), with stops at and Blenheim, taking a total flying time of about 4 hours 40 minutes, marking a significant milestone in aviation history. This crossing overcame challenging winds and demonstrated the feasibility of aerial travel over the strait, paving the way for regular services that began in the 1930s. Early commercial operations, such as those by Cook Strait Airways, connected with Nelson and Blenheim using Rapides, reducing travel time compared to sea voyages. Today, provides frequent domestic flights across Cook Strait from Wellington International Airport to key destinations, including Blenheim and Nelson, with typical durations of 25 to 30 minutes for the shorter routes. These services operate multiple daily frequencies—up to 11 to Blenheim and 14 to Nelson—using turboprop and jet aircraft like the and , accommodating both passengers and limited freight. In contrast, ferry services remain the primary mode for vehicles and rail freight but offer slower crossings of about three hours. In 2025, Air New Zealand initiated trials of electric aircraft in partnership with BETA Technologies, deploying the ALIA CX300—a battery-electric, fixed-wing model capable of carrying up to five passengers—for short regional hops, including potential Cook Strait routes. The aircraft, which arrived in New Zealand in October 2025, completed initial test flights from Hamilton and Tauranga, with plans for Wellington-based operations to evaluate zero-emission feasibility amid the strait's variable weather. These trials aim to decarbonize short-haul aviation, building on the ALIA's 280-nautical-mile range and rapid 60-minute recharge. Beyond aviation, coastal shipping serves as an alternative mode for , circumventing direct Cook Strait crossings via longer routes such as Whanganui to Nelson, which could reduce reliance on the strait amid seismic risks. Proposals for high-speed have been discussed to enhance these bypass options, offering faster coastal freight delivery—potentially halving times compared to traditional vessels—though past Cook Strait catamaran services faced operational challenges like high fuel costs and weather sensitivity. Air links across Cook Strait play a vital economic role, particularly in supporting by enabling quick access to Marlborough wine regions and Tasman Bay attractions, with handling over 4.5 million domestic passengers annually, a substantial portion of which involves crossings. This connectivity facilitates seasonal peaks, contributing to New Zealand's $40 billion sector, though exact strait-specific figures remain integrated within broader domestic traffic data.

Maritime Incidents and Safety

Cook Strait has been the site of numerous maritime disasters due to its challenging conditions, with over 1,000 shipwrecks recorded in the area since 1800. Among the most tragic incidents was the sinking of the inter-island ferry SS Penguin on 12 February 1909, when the vessel struck rocks near Cape Terawhiti in heavy seas and gale-force winds, resulting in 75 deaths out of 105 people on board. Nearly six decades later, on 10 April 1968, the TEV Wahine encountered a severe storm while approaching Wellington Harbour, grounding on Barrett Reef and capsizing, which claimed 53 lives from the 734 passengers and crew. More recently, the Interislander ferry Aratere experienced multiple groundings, including one on 21 June 2024 north of Picton during a voyage from Picton to Wellington, caused by a failure in the steering control system that the crew could not override, though no injuries occurred among the 47 people on board. These accidents are often attributed to the strait’s environmental hazards, including rogue waves, strong tidal currents, and persistent that reduce visibility. Rogue waves, which can reach up to 15 meters or more in height, arise from the interaction of swells and opposing winds in the narrow channel, while tidal currents reaching speeds of up to 6 knots exacerbate navigational difficulties by creating unpredictable eddies. , particularly in the cooler months, forms due to the mixing of warm air over cold currents, contributing to collisions and groundings. To mitigate these risks, New Zealand authorities have implemented several safety measures, including Vessel Traffic Services (VTS) radar systems operated by Ports of Wellington and other regional ports to monitor vessel movements and provide real-time guidance. , the national meteorological service, delivers specialized for Cook Strait crossings, issuing warnings for swells over 4 meters and wind speeds exceeding 30 knots that could impact ferry operations. Additionally, mandatory pilotage is required for vessels over 500 gross tons in adjacent sounds like Queen Charlotte Sound and Tory Channel to assist with through confined waters influenced by tidal dynamics. In 2025, events continued to pose challenges, with multiple sailings cancelled in August due to strong southerly winds and swells up to 5 meters, affecting both and Bluebridge services without resulting in fatalities but causing significant economic disruptions through delays and rebookings for thousands of passengers. Proposals for a fixed link across Cook Strait date back to the early , when Premier advocated for a bridge to connect the North and South Islands, envisioning it as a means to unify the nation economically and infrastructurally. This idea gained renewed attention in the mid- amid discussions on improving inter-island transport, though engineering assessments at the time, including a 1958 government inquiry, ultimately favored roll-on/roll-off rail ferries over a permanent structure due to practical constraints. In the 2010s, conceptual studies re-emerged for a submerged , estimated at approximately 25-30 kilometers in length to navigate the , with projected costs ranging from NZ$40 billion to NZ$50 billion. These proposals were largely dismissed following evaluations that highlighted insurmountable challenges, including the strait's high along the Pacific-Australian plate boundary, extreme tidal currents exceeding 4 knots, and water depths reaching up to 300 meters, which would complicate construction and maintenance. More recent assessments in 2024 and 2025, led by the Ministry of Transport, have reviewed options for resilient inter-island connections as part of broader planning, emphasizing the need for reliable freight and passenger links amid vulnerabilities exposed by disruptions. While favoring enhanced services as the primary solution, these evaluations have explored hybrid approaches, such as combining improved maritime operations with potential fixed elements like utility-integrated causeways, though full-scale bridges or tunnels remain unviable due to ongoing environmental concerns, including disruptions to marine ecosystems and migratory species. Existing continues to serve as the interim backbone for transport across the strait.

Infrastructure and Energy

Submarine Cables

The first across Cook Strait was a telegraph line laid in , connecting Lyall Bay in on the to Whites Bay near Blenheim on the , enabling instant communication between the islands for the first time. This simple copper cable, approximately 40 km long, faced significant challenges during installation due to strong currents causing the cable to snap, requiring a second attempt and use of recycled cable to complete the connection. Modern fiber-optic submarine cables for and connectivity were introduced across Cook Strait in the 1990s. In 1991, five new submarine cables, including fiber-optic for , were laid, followed by two more in 1992, often bundled with power infrastructure and forming a critical backbone for New Zealand’s digital connectivity, carrying vast amounts of between the islands. In 2020, a new 40 km cable was laid from Oteranga on the to Fighting on the at a cost of up to $15 million to replace end-of-life systems, designed to withstand the strait's tidal movements. The primary submarine power infrastructure consists of (HVDC) cables installed under the HVDC Inter-Island link, which began operations in 1965 with Pole 1 to transmit from the energy-rich to the . Pole 2 followed in 1992, with each pole rated at approximately 500 MW capacity, enabling a total transfer of up to 1,000 MW and supporting national grid stability by balancing supply across the islands. These three undersea cables, spanning about 40 km, are armored to withstand the strait’s conditions but have faced outages from faults and environmental stresses. In September 2025, Transpower submitted a $1.1 billion proposal for the first stage of the HVDC link upgrade, including replacement of the three aging cables by 2031, addition of a fourth cable, and upgrades to converter stations and control systems to boost overall capacity to 1,400 MW and enhance grid resilience. Laying and maintaining these cables presents significant challenges due to Cook Strait’s powerful tidal currents, which can reach speeds of 4-6 knots and cause scour, necessitating specialized vessels for precise installation and burial in water depths up to 200 m where feasible. In rocky areas, cables are often surface-laid with protective armoring rather than buried, and a designated Cable Protection Zone restricts activities like anchoring to minimize damage.

Tidal Energy Potential

Cook Strait's tidal streams offer substantial renewable energy potential, estimated at up to 12 GW, driven by peak current speeds exceeding 2.5 m/s in areas suitable for deployment. These strong, predictable flows, funneled by the strait’s narrow , position it among New Zealand's premier sites for tidal stream generation, with resource densities reaching over 5,000 /m² at select locations. A key proposed project was the Neptune Power initiative, which received resource consent for a 1 MW prototype horizontal-axis tidal turbine trial off Sinclair Head, intended to test feasibility and environmental effects but ultimately not constructed. Feasibility studies by the National Institute of Water and Atmospheric Research (NIWA) have evaluated tidal stream viability, focusing on optimization for economic and environmental in the strait. The primary technology for harnessing this potential involves seabed-anchored horizontal-axis turbines, akin to European designs like the UK's , which feature three-bladed rotors to capture bidirectional flows. Environmental impact assessments are integral, addressing risks such as collision with marine mammals, including dolphins and whales that traverse the strait. Significant barriers include high development costs, estimated at around NZ$500 million for a 100 MW farm, alongside challenges from marine mammal interactions and the need for high-voltage direct current (HVDC) integration to connect remote generation to the national grid. Existing submarine power cables across the strait facilitate potential transmission pathways.

Recreation and Challenges

Swimming Crossings

The first verified modern crossing of Cook Strait was achieved by Barrie Devenport on 20 November 1962, when he swam 22 km from the to the in 11 hours and 20 minutes, following numerous prior failed attempts by others since the . Devenport's success marked the beginning of documented solo swims across the strait, a challenging 20-30 km route depending on currents, governed by strict rules to ensure safety and ratification. Since then, approximately 207 successful solo crossings have been recorded as of April 2025, with swimmers facing a success rate of about one in six due to the strait's unpredictable conditions. New Zealand long-distance swimmer Philip Rush holds the record for the most crossings, completing eight between 1980 and 1988, including double and triple relays. His fastest solo time was 7 hours 51 minutes on 13 March 1984, from the to the , showcasing exceptional endurance in tidal flows that can extend the effective distance. The youngest successful swimmer is Aditya Santosh Raut, an 11-year-old from , who crossed from the to the on 20 2005 in 9 hours and 9 minutes. Swimmers encounter severe challenges, including cold water temperatures of 12-15°C that risk without wetsuits, which are prohibited under standard rules. Strong tidal currents reaching up to 5 knots can push swimmers off course or add hours to the journey, while stings are common, causing pain and inflammation. Shark encounters occur in about one in six attempts, necessitating vigilant watches from support boats equipped with spotters and electronic deterrents. All attempts are organized through the New Zealand Open Water Swimming Association (NZOWSA), which ratifies swims and enforces protocols such as non-wetsuit swims, no propulsion aids, and mandatory support vessels for navigation and emergency response. Permits are required from Maritime New Zealand to coordinate with shipping traffic in the busy strait, ensuring compliance with safety bylaws during the optimal February-April window.

Other Activities and Risks

Cook Strait supports a variety of recreational activities centered on its rich marine environment, including wildlife viewing, , , and . Wildlife viewing tours, particularly for marine mammals and seabirds, are popular, with operators offering cruises from ports like Picton and to observe species such as dusky dolphins, bottlenose dolphins, Hector's dolphins, New Zealand fur seals, and migratory humpback whales during winter months ( to ). These tours often highlight the strait’s role as a key and migration corridor, where participants may also spot with wingspans exceeding 3 meters and other seabirds like white-fronted terns. Recreational fishing is another prominent activity, with charters targeting species such as snapper in shallower waters and like hapuku, bass, and bluenose in the outer reaches. Access points include Wellington Harbour and the , where anglers use boats to reach productive sites, adhering to regulations that include size limits, bag limits, and closed areas to protect stocks. Scuba diving opportunities exist around wrecks and reefs in the , influenced by Cook Strait's currents, where divers encounter diverse including fish schools and forests, though conditions can vary due to water flow from the strait. Sea kayaking is pursued in sheltered areas near the strait, such as the sounds, with guided tours providing access to coastal scenery and , but full crossings are rare and reserved for experienced paddlers. These activities carry significant risks due to Cook Strait's dynamic conditions, including strong tidal currents reaching up to 4 knots and frequent tidal rips, particularly between Cape Terawhiti and Sinclair Head, which can capsize small vessels or kayaks. Northerly winds often exceed 30 knots near Rock and Sinclair Head, creating rough seas and reduced visibility that demand vigilant weather monitoring via VHF radio on Channel 14. For boating and fishing, reliable engines, lifejackets, and communication devices are essential, as is avoiding crossings during adverse forecasts; divers and kayakers face additional hazards from unpredictable swells and cold water temperatures averaging 13–15°C. Encounters with large ferries pose collision risks in busy channels, underscoring the need for all participants to carry safety gear and check tide charts beforehand.

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