(ARC-1: dp. 1,095 (f.); l. 203-6-; b. 34-6-; dr. 7-4-; s. 12 k.; cpl. 59; a. 1 40mm., 4 20mm.; cl. LSM-1)
In Roman mythology, a god of the sea, having jurisdiction over the ports and shores.
The second Portunus (ARC-1) was laid down by the Federal Shipbuilding and Drydock Co., Newark, N.J., as LSM-275 1 August 1944; launched 11 September 1944; and commissioned 6 October 1944.
After shakesdown off Norfolk, LSM-275 steamed for Key West, the Panama Canal, and San Diego before reaching Pearl Harbor 28 January 1945. After a trip to Guam she steamed from Pearl Harbor in TU 51.13.4 via Eniwetok and Saipan to Okinawa to land troops and supplies on the "last stepping stone" to Japan. Departing in TU 51.29.22, 25 April while the battle for Okinawa was still going on, she steamed via Saipan to Ulithi, arriving 5 May. Departing 28 June she then put into Tulagi, the Russells, Eniwetok, Guam, and Saipan, before reaching Pearl Harbor 19 August, 5 days after the war's end.
On 4 December she departed Pearl Harbor for San Diego. She steamed between San Diego, San Pedro, and San Francisco during the first half of 1946, then reported to Com 19th Fleet at San Diego 18 September; underwent inactivation overhaul; and decommissioned 21 April 1947 at San Pedro.
Ordered activated in 1951, LSM-275 was redesignated as a cable laying and repair ship ARC-1 on 14 December, and recommissioned 2 July 1952. She operated off California ports for the next 11 months, then, on 1 June 1953, got underway for the east coast. The ship was named Portunus 13 July 1953. Attached to the 3rd Naval District, she laid cable off Cape May, N.J., and off Bermuda before conducting ocean bottom surveys and cable operations off Columbia-s Atlantic and Pacific coasts, 13 October to 31 October.
Returning to New York, Portunus underwent overhaul and on 8 March 1954 resumed cable operations, first in the approaches to New York, off Sandy Hook, N.J., then off Bermuda. From 1955 to 1959 she continued to lay cable, off Key West, off Sandy Hook, off Bermuda, off Wood Island, Maine, off Nantucket Island, in the Narragansett area, and off Little Creek, Va. During this period she continued to base at the New York Shipyard, Brooklyn, and to periodically pick up cable at Newington, N.H. She decommissioned at New York 30 April 1959, and her name was struck from the Navy List 1 May 1959.
She was transferred to Portugal under the Military Assistance Program; delivered on 16 November 1959; and commissioned 18 November as Medusa (A 5214). Into 1970 she serves in the Portuguese Navy.
Portunus earned one battle star for World War II service.