[1][5] 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.

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.

[6] In 1914, World War I broke out and Scouts across the country found themselves becoming involved on the home front with non-militarised service.

[8] 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.

The Sea Scouts still has access to TS Mercury but in 1936 the RRS Discovery, the ship that had taken Robert Falcon Scott to Antarctica for his disastrous South Pole expedition, was offered to the association and was promptly bought in January 1937 following a donation from Lucy, Lady Houston.

[5] Notably, the 1st Mortlake Sea Scouts took their motor picket-boat Minotaur to France as part of the Dunkirk evacuation in 1940.

[13] With bombing of towns and cities across Britain as part of the Blitz, Scouts also took on roles helping during the air-raid; George Collins, a Patrol Leader with the 12th Shoreditch Sea Scouts was awarded a Silver Cross for bravery when he rescued three children from a house in Barnet during bombing on 8 October 1940.

The following year a Sea Scout Exhibition took place from 10–19 April at the Scottish Drill Hall and attended by Princess Elizabeth.

[5] Sea Scouts were also involved in the 1948 Summer Olympics with 200 helping to ferry competitors between boats and jetties near the sailing events in Torbay.

In 1954, the RRS Discovery was transferred back to Royal Navy ownership when the Scouts could no longer afford the upkeep.

[5] and in 1968 the TS Mercury was retired[5][16] To compensate, in 1956, Marlow, Buckinghamshire on the River Thames became home to Longridge Scout Boating Centre to train in seamanship and other water sports.

This has developed from a wooden pavilion, derelict warehouse and a small fleet of dinghy boats in the area now occupied by Canary Wharf to a metal cutter the Lord Amory and a new boathouse complex acquired in 1981 and 1994 respectively.

The Centenary Sea Scout Jamboree was held in August of that year, at the Holme Pierrepont National Watersports Centre in Nottinghamshire.

[19][20] The centenary of Royal Naval recognition in 2019 was also celebrated by the Scouts with an occasional badge that could be worn on uniforms being released.

Members of both make the same promise as any other Scout or Explorer Scout and take part in the same wider programme based on the themes of Outdoor and Adventure, World and Skills, although the nautical elements of this programme tend to be the focus of activities especially in the summer months when the weather is fine enough for boating outdoors.

[22] They are led locally by a volunteer manager, called a Group Scout Leader, and are responsible for ensuring the standards of the section are maintained.

[24] The scheme began in 1919 following the efforts of Scouts during World War I in support of the armed forces, through service as coast watchers, first aiders, fire fighters and messengers.

[24] Recognised Groups are entitled to fly a Red Ensign[25] and blue pennant, both defaced with a Scout arrowhead and Admiralty crown.

The decline in British shipping numbers, both naval and merchant, in the late 20th century was reflected in a reduction in membership of the Deep Sea Scouts.