which had sunk on the evening of 24 January after the submarine chaser PC-460 accidentally rammed her. In June 1942, S-21 returned to New London. On 14 September 1942, she was decommissioned. Royal Navy On the day of her decommissioning, S-21 was transferred to the United Kingdom. As HMS P.553, she served in the Royal Navy until returned to the U.S. Navy at Philadelphia on 11 July 1944. Disposal After her return, the U.S. Navy used S-21 as a target. She was sunk in of water in the Atlantic Ocean off Cape Elizabeth, Maine, on 23 March 1945. References External links Naval Oceanographic Office - Historical Timeline Plate tectonics: an insider's history of the modern theory of the Earth, by Naomi Oreskes, Homer Eugene LeGrand Eagle Class Patrol Vessel (PE) description United States S-class submarines Ships built in Quincy, Massachusetts 1920 ships World War II submarines of the United States Ships transferred from the United States Navy to the Royal Navy United States S-class submarines of the Royal Navy World War II submarines of the United Kingdom Ships sunk as targets Maritime incidents in March 1945 Shipwrecks of the Maine coast