(SP-710: t. 53; l. 98'; b. 14'; dr. 5'9"; s. 10 k.; cpl. 19; a. 1 6-pdr., 1 .30 cal. mg.)
A precious stone of transparent rich blue corundum. Sapphire (SP-710) retained her mercantile name in United States Naval service.
On 8 June 1917, after the United States entered World War I, Sapphire (SP-710), a single-screw, wooden yacht built in 1900 by Herreshoff Mfg. Co., Bristol, R.I., was enrolled in the Naval Coast Defense Reserve by her owner, Jeremiah Milbank of New York City; and commissioned on 14 September 1917 at Brooklyn, N.Y., Ensign John J. Montgomery, USNRF, in command.
After fitting out for naval service at Tebo's Yacht Basin, Sapphire joined the Section Patrol of the 3d Naval District on 14 July 1918. Sapphire patrolled the waters off Execution Light, alternating with or joining Sturdy (SP-82), Jimetta (SP-878), and Josephine (SP-913). Inactive from 20 November 1918, she was transferred from Section Base No. 7 to New York harbor on 10 December 1918.
Sapphire was towed by Minerva (SP-425) to Robert Jacob's shipyard on 16 December 1918, decommissioned, and returned to her owner the same day.