USS R-18 (SS-95) was an R-class coastal and harbor defense submarine of the United States Navy. Construction and commissioning R-18′s keel was laid down on 16 June 1917 by the Union Iron Works in San Francisco, California. She was launched on 8 January 1918, sponsored by Miss Marion S. Russell, and commissioned on 11 September 1918. Service history 1918–1931 Following shakedown, R-18 was assigned, briefly, to the Panama Canal Zone. At the end of 1918 she returned to California. She was at San Pedro, California, from January to March 1919, then underwent an overhaul at San Francisco. On 17 June 1919 she got underway for Hawaii and on 25 June 1919 she arrived there at Pearl Harbor. Based there for over a decade, she served with the United States Pacific Fleet, training personnel and testing new submarine equipment. On 17 July 1920 she was given the hull classification symbol SS-95. R-18 departed Hawaii on 12 December 1930, transited the Panama Canal, and thence continued on to the United States East Coast for inactivation. Arriving at Philadelphia, Pennsylvania, on 9 February 1931, she was decommissioned on 13 May 1931 and berthed at League Island. 1941–1946 Recommissioned 8 January 1941, R-18 was at New London, Connecticut, for reconditioning and fitting out into May 1941. On 12 May 1941 she got underway for the Panama Canal Zone, where she patrolled into September 1941. In October 1941 she returned to New London, underwent an overhaul, and then conducted training exercises in submarine warfare and anti-submarine warfare. In early January 1942, she shifted her training activities to the Casco Bay, Maine, area. Then, later January 1942, she added patrols along a line between Nantucket Light and Bermuda to her schedule. Originally patrolling from New London, she shifted to Bermuda in May 1942. On 30 May 1942, a U.S. Navy OS2U-2 Kingfisher floatplane mistook her for a German U-boat and dropped a depth charge on her as she crash-dived in the Atlantic Ocean bearing 50 degrees from Bermuda′s Mount Hill Lighthouse. R-18 sustained no damage. In August 1942 she moved farther south and until December 1942 operated in a training capacity in the United States Virgin Islands and at Trinidad. Then assigned with other R-class submarines to training duties for the remainder of World War II, R-18 returned to New London on 24 December 1942. She operated in the New London and Portland, Maine, areas until