Operation Jaywick was a special operation undertaken in the Second World War. In September 1943, 14 commandos and sailors from the Allied Z Special Unit raided Japanese shipping in Singapore Harbour, sinking three ships and damaging three more using limpet mines.

Special Operations Australia (SOA), a combined Allied military intelligence organisation, was established in March 1942. SOA operated under the cover name Inter-Allied Services Department (IASD). It contained several British SOE officers who had escaped from Japanese occupied Singapore, and they formed the nucleus of the IASD, which was based in Melbourne. In June 1942, a commando arm was organised as Z Special Unit (which was later commonly known as Z Force). It drew its personnel primarily from the Australian Army and Royal Australian Navy.

In 1943, a 28-year-old British officer, Captain (later Major) Ivan Lyon (of the Allied Intelligence Bureau and Gordon Highlanders), and a 61-year-old Australian civilian, Bill Reynolds, devised a plan to attack Japanese shipping in Singapore Harbour. Commandos would travel to the harbour in a vessel disguised as an Asian fishing boat. They would then use folboats (collapsible canoes) to attach limpet mines to Japanese ships.

Initial training for the raid was organised and carried out by Major Lyon and Captain Davidson at Refuge Bay. The site selected was a remote, inaccessible area along the Hawkesbury River, New South Wales and named Camp X. Folboats were essential for training the prospective operatives but only two, a one-man and a two-man were found to be suitable after a thorough search in Australia by military personnel. These were bought on the spot from the folboat builder Walter Hoehn after a test run on the Yarra River, Alphington by the head of the Inter Allied Services Department, Colonel Mott and Major Moneypenny. A wooden rigid canoe was also built for Camp X by trainees under the supervision of Davidson.

Reynolds was in possession of a 21.3-metre (70 ft) Japanese coastal fish carrier, Kofuku Maru 幸福丸, which he had used to evacuate refugees from Singapore and its neighboring islands. Lyon ordered that the boat be shipped from India to Australia. Upon its arrival, he renamed the vessel Krait, after the krait a small but deadly Asian snake.

In mid-1943, Krait travelled from a training camp at Broken Bay, New South Wales to Thursday Island. Aboard was a complement from Z Special Unit of three British and eleven Australian personnel, comprising:

On 13 August 1943, Krait left Thursday Island for Exmouth Gulf, Western Australia, where it was refuelled and repairs were undertaken. The repairs caused delays in departure and the folboats, manufactured by Harris Lebus, called model MKI**, which had been specially ordered for the attack by Lyon from England only arrived at the last minute. They were found to be faulty, lacked some important parts and were not according to the design that Davidson had specified. They had to undergo many changes to make each framework fit together and then fit correctly into the outer skins. This left the crew little time to get accustomed to them before being loaded on to Krait.

On 1 September 1943, Krait left Exmouth Gulf and departed for Singapore. The team's safety depended on maintaining the disguise of a local fishing boat. The men stained their skin brown with dye to appear more Asiatic and were meticulous in what sort of rubbish they threw overboard, lest a trail of European garbage arouse suspicion. During the journey, they suffered a snapped propeller shaft, which had to be repaired by a passing US submarine, while the heavily laden craft was later almost sunk by a force nine gale. Krait arrived off Singapore on 24 September. That night, six men left the boat and paddled 50 km (31 mi) with folboats, to establish a forward base in a cave on a small island near the harbour. On the night of 25/26 September 1943, they paddled into the harbour and placed limpet mines on several Japanese ships before returning to their hiding spot.