USS S - 21 ( SS - 126 ) 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 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 . Service history . 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 . " S - 21 " served again in the Panama Canal area from March into April 1929 , and from January through February 1930 . Departing New London on 22 October that year , " S - 21 " sailed via the Panama Canal and California to Pearl Harbor , arriving on 7 December . From 1931 into 1938 , " S - 21 " operated from Pearl Harbor , with the period 18 November 1932 to 24 January 1934 spent in reserve . Departing Pearl Harbor on 15 October 1938 , she sailed via California and the Panama Canal to Philadelphia , Pennsylvania , arriving on 11 December . Following overhaul she arrived at New London on 25 March 1939 . She remained at New London with a partial crew from 1 June of that year until 1 September 1940 , when she was returned to full duty . On 9 December , two days after the Pearl Harbor attack , " S - 21 " got underway for the Panama Canal Zone . Arriving ten days later , she conducted defensive patrols in the Pacific Ocean approaches to the canal through May 1942 . Her second such patrol , 24 January to 7 February , was cancelled to allow her to participate in search and rescue operations for submarine , which had been rammed by submarine chaser " PC - 460 " on the first day of the patrol . In June 1942 , " S - 21 " returned to New London . On 14 September , she was decommissioned and was transferred to the United Kingdom . As , she served in the Royal Navy until returned to the United States Navy , at Philadelphia , on 11 July 1944 . Subsequently used as a target , she was sunk off northern New England on 23 March 1945 . USS " S - 21 " : First U . S . Gravity Measurements at Sea . The first U . S . gravity measurements at sea were made from the USS " S - 21 " assisted by Eagle Boat " 35 " and Eagle Boat " 58 " . After the first gravity measurements at sea had been made in 1926 from a submarine of the Royal Navy the Carnegie Institution proposed the U . S . take Caribbean Sea measurements using a gravimeter , or gravity meter , designed by Dr . Felix Vening Meinesz . Such measurements required the stability and lack of motion only attainable at sea on a submerged submarine . With assistance from the National Academy of Sciences , the U . S . Coast and Geodetic Survey , the U . S . Naval Observatory and U . S . Navy Hydrographic Office the expedition was arranged . Special chronometers necessary for the observations were furnished by the Naval Observatory . Dr . Meinesz accompanied the expedition with Elmer B . Collins representing the Hydrographic Office aboard S - 21 with the Eagle Boats serving as tenders . The route was from Hampton Roads starting 4 October 1928 and return by way of Key West , Florida , Galveston , Texas , Guantanamo , Cuba , the Virgin Islands and Puerto Rico with the return to Hampton Roads on 30 November 1928 . The first of forty - nine gravity measurement stations was located at 36°56 . 7 ′ N 76°19 . 19 ′ W . The gravity measurements were accompanied by a sonic depth sounding with results published on a chart produced by the U . S . Navy Hydrographic Office . The gravity measurements were utilized in determining the shape of the Earth and of particular interest were the negative gravity anomalies . The results of this expedition , particularly the significant negative anomalies , created interest in a second expedition resulting in the Navy - Princeton gravity expedition to the West Indies in 1932 using the submarine USS " S - 48 " . That was in turn followed by a third measurement effort using on the Gravimetric Survey Expedition .