The USS Tourmaline (PY-20) was a converted yacht built in 1930 at Bath, Maine, by Bath Iron Works, originally named Sylvia. She was purchased by the U.S. Navy on 16 May 1941 from Logan G. Thomson of Grand Haven, Michigan, and underwent conversion at the Marine Basin Co. in Brooklyn, New York, before being commissioned as USS Tourmaline on 19 September 1941 at the New York Navy Yard. Designed as a patrol vessel, Tourmaline was relatively modest in size, having been originally a private yacht, but was adapted for wartime service. She departed New York on 2 October 1941 for Norfolk, Virginia, and operated out of Hampton Roads during the final months of the U.S.’s pre-war period. Following the attack on Pearl Harbor, she commenced her wartime patrols along the U.S. East Coast, particularly near Norfolk and Charleston, South Carolina. Throughout her service, Tourmaline was engaged in convoy escort duties and patrols across the Atlantic and Caribbean waters. Notably, on 15 April 1942, she was patrolling near Chesapeake Bay when the submarine USS Mackerel contacted her regarding a sighting of a German U-boat, which she attempted to track without success. She also escorted merchant convoys between key ports such as Key West, Norfolk, and Trinidad, and participated in patrols near Cuba and the West Indies. In December 1942, she experienced an engagement when her sonar detected a strong metallic echo, leading to a depth charge attack—though she was forced to break off when her steering gear was damaged. She continued convoy escort duties until January 1944, after which she joined the Naval Local Defense Force based in Boston. She patrolled off Massachusetts through the end of World War II. Decommissioned on 18 July 1945, USS Tourmaline was struck from the Navy list in August and transferred to the War Shipping Board in January 1946. She was subsequently purchased by Greek organizations, reverting to her original name, Sylvia, marking her transition from military service back to civilian use.

This description has been generated using GPT-4.1-NANO based on the Vessel's wikidata information and then modified by ShipIndex.org staff.