USS S-21 (SS-126)

S-21 at Coco Solo, Panama Canal Zone, c.1927
History
United States
Name:	USS S-21
Builder:	Bethlehem Shipbuilding Corporation
Laid down:	19 December 1918
Launched:	18 August 1920
Commissioned:	24 August 1921
Decommissioned:	14 September 1942
Fate:	Transferred to the Royal Navy, 14 September 1942 Returned, 11 July 1944 Sunk as a target, 23 March 1945
United Kingdom
Name:	HMS P.553
Acquired:	14 September 1942
Fate:	Returned to the US Navy, 11 July 1944
General characteristics
Class and type:	S-class submarine
Displacement:	854 long tons (868 t) surfaced 1,062 long tons (1,079 t) submerged
Length:	219 ft 3 in (66.83 m)
Beam:	20 ft 8 in (6.30 m)
Draft:	15 ft 11 in (4.85 m)
Speed:	14.5 knots (16.7 mph; 26.9 km/h) surfaced 11 knots (13 mph; 20 km/h) submerged
Complement:	42 officers and men
Armament:	1 × 4 in (100 mm)/50 deck gun 4 × 21 inch (533 mm) torpedo tubes

USS S-21 (SS-126) was a first-group (S-1 or "Holland") S-class submarine of the United States Navy. Her keel was laid down on 19 December 1918 by the Bethlehem Shipbuilding Corporation's Fore River Shipyard in Quincy, Massachusetts. She was launched on 18 August 1920 sponsored by Mrs. Thomas Baxter, and commissioned on 24 August 1921 with Lieutenant R. P. Luker in command.

Following operations from New London, Connecticut, S-21 was decommissioned and returned to her builder on 31 March 1922. After she was reacquired by the Navy, S-21 recommissioned at Groton, Connecticut, on 14 September 1923 with Lieutenant Commander Palmer H. Dunbar, Jr., in command. From 1923 into 1930, S-21 operated off the northeastern coast of the United States. From January into April 1924, she visited the Panama Canal, Saint Thomas, United States Virgin Islands, and Trinidad. Departing from New London on 25 November, she visited Hawaii, from 27 April to 25 May 1925, before returning to New London in July. Following duty in the Panama Canal area, from February through April 1926, she visited Kingston, Jamaica, from 20 to 28 March 1927. The submarine operated in the Panama Canal area, from February into April 1928. From 4 October 1928 until 30 November 1928 S-21 was the vessel used in the first gravimetric observations at sea made by the United States.