AVP-51
Displacement 2,592
Length 310'9"
Beam 41'2"
Draw 13'6"
Speed 18.2 k
Complement 215
Armament 1 5", 8 40mm
Class Barnegat

San Carlos (AVP-51) was laid down on 17 September 1942 by the Lake Washington Shipyard, Houghton, Wash.; launched on 20 December 1942; sponsored by Mrs. Henry D. Batterton; and commissioned on 21 March 1944, Lt. Comdr. De Long Mills in command.

After shakedown, San Carlos, a small seaplane tender, departed southern California on 1 June 1944. Arriving at Green Island on 25 June, she engaged in air-sea rescue operations in the northern Solomons from the 26th to 3 September, and at Morotai Island, shortly after its capture, from the 18th to the 30th.

Arriving off Leyte, P. I., on 18 October, at the beginning of the campaign to liberate the Philippines, she fueled battleship and cruiser observation planes, and splashed one enemy plane on the 21st. Arriving at San Pedro Bay, Leyte on the 24th, she downed an enemy plane on the 21th, and tended patrol planes. Departing on 4 November, she made a cargo trip to Humboldt Bay, New Guinea, returning to San Pedro Bay on the 18th. Arriving at San Juanico Strait on the 22nd, she shot down another enemy plane on the 26th and tended seaplanes there until 22 January 1945. After duty at Mindoro Island in February, she tended planes near Cavite, Luzon, from March until 11 August.

She arrived at Bremerton, Wash., on 3 September. After overhaul, she operated out of Coco Solo Panama Canal Zone, from December through May 1946, and out of San Juan, Puerto Rico, from July into March 1947. Decommissioned on 30 June at Philadelphia, she entered the Atlantic Reserve Fleet.

Reactivated in 1958, San Carlos was taken out of the Reserve Fleet on 11 July and assigned to the Military Sea Transportation Service for conversion to an oceanographic research ship by the Mobile Ship Repair Co., Mobile, Ala. On 15 December 1958, she was renamed Josiah Willard Gibbs (in honor of the 19th Century mathematician and theoretical physicist) and reclassified AGOR-1. Three days later, on 18 December, she was placed in service.

As an AGOR, the ship has a crew of 48 and a scientific staff of 24. Alterations to her original design included the installation of six laboratories, a machine shop, a darkroom, and a superstructure deck locker for experimental stowage or work, a deep sea winch capable of handling up to 40,000 feet of wire rope and 20 tons of equipment.

After fitting out, the new AGOR, an MSTS ship, became the principal research vessel of the Hudson Laboratories of Columbia University, under contract to the Office of Naval Research; and, through the next decade, provided transportation, accommodations, and working spaces for American scientists and technicians investigating physical, chemical, and biological properties of the ocean. On 15 December 1971, she was transferred to Greece and renamed Hephaisto. Since then, into 1974, she has provided similar services to scientists of that country.

San Carlos received three battle stars for World War II service.