USS San Carlos (AVP-51) was a Barnegat-class seaplane tender built for the United States Navy during World War II. San Carlos, named after San Carlos Bay, Florida, was in commissioned from 1944 to 1947 and earned three battle stars for service in the Pacific during World War II. After eleven years in reserve, San Carlos was converted to oceanographic research ship USNS Josiah Willard Gibbs (T-AGOR-1)—named after American scientist Josiah Willard Gibbs—and placed in service as a non-commissioned ship of the Military Sea Transportation Service from 1958 to 1971. In December 1971, the ship was transferred to the Hellenic Navy as Hephaistas (A413), a motor torpedo boat tender. Hephaistas was struck from the rolls of the Hellenic Navy in April 1976.