The Scout Association's Sea Scouts are a branch of the association dedicated to boating and water-based activities such as sailing, canoeing, motorboating and water navigation. The association approved a special uniform for Sea Scouts in 1910 and, in 1912, the association formally adopted use of the name "Sea Scouts". Specialist Sea Scout troops have existed ever since. They are usually based by the side of water, either the sea, lake, river or canal.

Sea Scouts may be organised as Sea Scout Groups, where there is a nautical focus for all sections offered by the group, or as individual Sea Scout troops within a larger group that may not share the same nautical focus. In a Sea Scout Group, only the members in Sea Scout troops (10½-14 years of age) and Sea Explorer units (14–18 years of age) wear a different uniform and follow a more nautical focus within the current Scout programme while younger members, in the Squirrel (4-6 years of age), Beaver (6–8 years of age) and Cub (8-10½ years of age) sections, follow the same programme and wear the same uniform as non-Sea Scout Scout Groups. With the exception of Air Scouts, Sea Scouts are the only part of the association that wears hats as part of their official uniform.

For the history of Sea Scouts generally and prior to The Scout Association adoption of its own Sea Scout program see Sea Scouts.

The association approved a special uniform for Sea Scouts in 1910 with a sou'wester hat for Sea Scouts involved in coast watching and a navy sailor cap for Sea Scouts involved in boating and, in 1912, the association formally adopted use of the name "Sea Scouts". Henry Warrington Smyth Baden-Powell, older brother of Robert, founded the branch and in 1912 would write the comprehensive manual Sea Scouting and Seamanship for Boys, a follow-up to the short booklet Sea Scouting for Boys published the previous year by his younger brother.

Water based activities had been a part of Scouting from its earliest years. Robert Baden-Powell wrote in his Scouting for Boys (published 1908) that 'a Scout should be able to manage a boat, to bring it properly alongside a ship or pier.' In February 1909 The Scout magazine reported the foundation of a new branch of Scouts around Glasgow who were referring to themselves as "Sea Scouts" stating they will be just the same as land Scouts but trained 'on a naval basis, learning naval drills and visiting His Majesty's ships whenever possible.' In June 1909 a Seamanship proficiency badge was introduced for all Scouts that allowed them to learn these skills. A camp took place in July to August 1909 on the ship TS Mercury, moored at Buckler's Hard, with 50 spent sleeping on the ship and another 50 spent camping on the shore before swapping after a week. The 100 places were allocated through a competition in the Scout magazine.

Very early on in the history of the association's Sea Scouts branch, it was hit by two accidents which resulted in the loss of several Sea Scouts' lives. The most prominent was the Leysdown disaster of 4 August 1912 when an ex-naval cutter carrying 23 Sea Scouts from Walworth, London, off the coast of Leysdown-on-Sea, Isle of Sheppey, capsized in a sudden storm. Despite the efforts of five coastguards and two civilians, nine of the Scouts drowned. A mass funeral was held on 10 August attended by thousands including Scouts from several countries. That same year the Sea Scouts of London were presented a 52 ton ketch yacht by the Daily Mirror newspaper and named Mirror. However just the following year the boat was struck by another vessel resulting in the loss of four lives. Following both these tragedies, new rules were put in place and training tightened but these did not deter the progress of the branch. In early 1914, the HQ Gazette announced that 'No boat training shall be undertaken unless the Scout can swim fifty yards' and the August 1914 published Seamanship for Scouts by Lt Cdr W. H. Stuart Garnett had a greater emphasis on safety management.

In 1914, World War I broke out and Scouts across the country found themselves becoming involved on the home front with non-militarised service. While Scouts took on roles guarding bridges, telegraph lines or culverts from damage and acting as messengers, Sea Scouts in particular took up a role across the country supporting the coast guard. With the Royal Navy on a war footing, Baden-Powell thought that getting scouts to watch estuaries, ports and from coastguard stations this could free up men needed for military service. Sea Scouts and other Scouts engaged in coast watching were supervised by the coastguard but were under the orders of the Patrol Leaders and many were already trained for the roles, a Coast Watcher badge having been introduced in 1911 to Admiralty standards. The call was a success with 1,300 Sea Scouts and other Scouts on coast watching duty within two months of the war's outbreak and 23,000 Scouts having been coast watchers during the course of the war. Specific duties included patrolling the beaches, salvaging wreckage, watching for fishing boats working unauthorised at night, examine boats coming into shore checking permits, answering naval calls on the telephone and report vessels passing up and down the coast.

In 1928 a new branch of Sea Scouts, the Deep Sea Scouts, was formed to enable young people who had begun a working life aboard ships to maintain connection with the association.