USS Halcyon (SP-518)

USS Halcyon (SP-518) was a motor launch borrowed by the U.S. Navy from the U.S. Bureau of Fisheries during World War I. She was outfitted as a patrol craft and assigned to the 1st Naval District, headquartered at Portsmouth Navy Yard in Kittery, Maine. Post-war she was returned to the Bureau of Fisheries.

Borrowed from Bureau of Fisheries
The first ship to be so named by the U.S. Navy, Halcyon was a 61-foot-long launch built for the Bureau of Fisheries in 1916 by Marine Construction Company, Boothbay Harbor, Maine. She was transferred to the Navy and commissioned 14 May 1917 at Boston, Massachusetts.

World War I service
Assigned to section patrol in the 1st Naval District, Halcyon performed harbor patrol duties until decommissioning 24 June 1919.

Post-war disposition
She was subsequently struck from the Navy List 31 July 1919 and returned to the Bureau of Fisheries.

Note
USS Surf (SP-518) was never commissioned. Her hull number (SP-518) was assigned to Halcyon.