USS Grayback ( SSG - 574 ) USS " Grayback " ( SS / SSG / APSS / LPSS - 574 ) , the lead ship of her class of submarine , was the second ship of the United States Navy to be named for the grayback , a small herring of commercial importance in the Great Lakes . 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 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 . Operational history . Guided missile submarine . The first of the Navy ' s guided missile submarines to carry the Regulus II sea - to surface missile , " Grayback " conducted tests and shakedown along the West Coast . While operating out of Port Hueneme , California , in September 1958 she conducted the first successful launching of a Regulus II missile from a submarine , which led to the capability of navies to attack land bases . Departing San Diego , California , on 30 October , " Grayback " arrived at Pearl Harbor on 8 November for a month of exercises and maneuvers before returning to Mare Island for her " 10 , 000 mile checkup . " On 9 February 1959 , " Grayback " departed Mare Island to make Pearl Harbor her permanent home base , reaching Hawaii on 7 March via Port Hueneme , California , Long Beach , California , and Mazatlan , Mexico . After a series of exercises there , she cruised to Dutch Harbor , Umak Island , Sequam Island , and Kodiak , Alaska , for further missile exercises from 3 – 31 July . This was followed by the first of her nine deterrent missile strike missions , from 21 September to 12 November . " Grayback " s first patrol terminated at Yokosuka , Japan , as did two others . She returned to Pearl Harbor 8 December . On 22 February 1960 , " Grayback " modified her missile launching system and simplified her complex electrical circuits . After this , she again took up deterrent missile strike missions . Over the next 2½ years she completed seven missions for a total of nearly 18 months at sea , much of this time submerged . In addition to Yokosuka , both Adak , Alaska , and Pearl Harbor also served as termination points for these patrols . On her nine patrols she spent more than 20 months at sea and logged over 130 , 000 miles ( 209 , 000 km ) on deterrent missile strike missions . That schedule took its toll . On 27 August 1963 , while snorkeling to recharge batteries , " Grayback " was buffeted by particularly strong seas . The buffeting caused the After Main Battery breaker to short , starting a fire in the berthing compartment . One seaman failed to evacuate the compartment and was overcome by smoke and fumes . Main propulsion was lost for a short time , was restored , and " Grayback " returned to Pearl Harbor under her own power . Repairs took two weeks . As more Polaris missile submarines became operational , they assumed the deterrent functions previously assigned to " Grayback " and her sister ships . The Regulus missile program ended in 1964 and " Grayback " was withdrawn from active service . She decommissioned at Mare Island Naval Shipyard , California , on 25 May 1964 . Amphibious transport submarine . 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 . 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 Vehicle s ( 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 . " 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 . References . < br > Gardiner , Robert . " Conway ' s All the World ' s Fighting Ships 1947 - 1995 . " London : Conway Maritime Press , Ltd , 1995 Pg . 609 - 610