page_title: USS Grayback (SSG-574)
section_title: Amphibious transport submarine
hierarchical_section_title: USS Grayback (SSG-574) / Operational history / Amphibious transport submarine
caption_attribution_description: English: The USNS Catawba (ATF-168) is seen towing the Ex-Grayback (LPSS-574) out of Subic Bay on 13 Aug 1986. The Grayback was painted orange for an impending sink excise.
context_page_description: USS Grayback, the lead ship of her class of submarine, was the second ship of the United States Navy to be named for the grayback.
  Her keel was laid down on 1 July 1954 by the Mare Island Naval Shipyard of Vallejo, California. She was launched on 2 July 1957 sponsored by Mrs. John A. Moore, widow of the last skipper of the USS Grayback and commissioned at Mare Island on 7 March 1958 with Lieutenant Commander Hugh G. Nott in command. Grayback was initially designated as an attack submarine, but was converted to a Regulus nuclear cruise missile submarine (SSG-574) in 1958.
context_section_description: A second conversion began at the Mare Island Naval Shipyard in November 1967. The conversion was originally estimated at US$15.2 million, but grew to over US$30 million. She was re-classified from a guided missile submarine to an amphibious transport submarine with hull classification symbol LPSS-574 on 30 August 1968. (The Naval Vessel Registry entry for Grayback shows that at one point she was classified as a "plain" transport submarine, an APSS. The term "APSS", for Auxiliary Personnel Submarine, appeared on the construction plans and documents during the conversion design and construction period (per Structural Naval Architect, Mare Island, 1966-1968). Crew memoirs indicated that they were never aware of it. Presumably, while this classification was "official," it may have lasted only days.)
  The conversion heightened her sail by ten feet, added two auxiliary tanks to the forward end of the engine room (increasing the length of the boat by 12 feet), and converted the missile chambers to carry 67 embarked troops and SEAL Swimmer Delivery Vehicles (SDVs), including a decompression chamber in the starboard hangar.
  In June 1972, the Grayback carried a team of Navy SEALs into the coastal waters of North Vietnam as part of Operation Thunderhead. This was the last attempt during the Vietnam War to rescue American POWs held in North Vietnam.
  In January 1982 five U.S. Navy divers died when a vacuum was inadvertently drawn in a chamber on Grayback off the coast of Subic Bay, P.I.  The diving accident led to changes in how the Navy designed, built, maintained and operated complex submarine based diving systems.
  Grayback was decommissioned for the second time on 15 January 1984 at Subic Bay Naval Station in the Republic of the Philippines. After decommissioning, Grayback was sunk as a target on 13 April 1986 in the South China Sea.
caption: Grayback painted orange for sinking
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