H.M.S. Reclaim was built in 1948 by Simons & Co. of Renfrew as a salvage ship of the King Salvor class but altered before completion for her role as a deep diving vessel. She established world deep diving records in 1948 (536 ft., 163 m.) in Loch Fyne, the diver wearing a standard diving dress and breathing a mixture of oxygen and helium, and in 1956 (600 ft., 183 m.) off Norway. In 1964 she carried out a series of dives to 600 ft. for one hour, off Toulon, the divers wearing lightweight self-contained equipment. In 1950 she located the sunk submarine Truculent in the Thames estuary and in 1964 the submarine Affray, when underwater television was used for the first time. In 1966 she recovered a crashed Viscount aircraft in the Irish Sea. Reclaim is now engaged in trials which will eventually permit diving for prolonged periods to 1000 ft., and therefore anywhere on the Continental Shelf.

Two divers are lowered to the sea-bed in a submersible compression chamber equipped with underwater lighting and television and in telephonic communication with the ship. While one diver swims out of the chamber to undertake the required task the other acts as attendant. The chamber when hoisted aboard under pressure is locked on to another chamber in the ship's hold, where the divers carry out the process of decompression which may take several hours.

H.M.S. Reclaim encounters some unique navigation and seamanship problems when engaged in deep diving.