Originally a private yacht and later a navy training vessel, Sapphire was built in 1929 and named Buccaneer by George Lawley & Son, Neponset, Massachusetts. It was acquired by the U.S. Navy from a later owner, Mr. Leon Mandel, Quonset, Massachusetts, on 1 November 1940. The navy renamed the boat Sapphire, designated it PYc—2, and converted it for Navy use. It was officially commissioned at Boston on 6 June 1941 with Lt. A. N. Daniels, USNR, in command.