The USS Sealion was the only US Submarine to sink a Battleship, the INJ Kongo, the ship was awarded the Presidential Unit Citation for her six war patrols, at the end of WW2 it was decommissioned.

A year and one-half later, however, USS Sealion, along with USS Perch (SS-313), supported Pacific region operation,  were both designated for conversion to troop carriers.

On 2 November 1948, Sealion was recommissioned with the hull designation SSP-315. The Sealion conducted training exercises off the southern California coast, with Marines embarked, 

On 31 January 1950, she was reclassified ASSP-315; and, by the spring of that year, had conducted exercises as far north as Labrador and as far south as the southern Caribbean. The Sealion continued a schedule of exercises with Marines, Underwater Demolition Teams and Beach jumper units; and, on occasion, Army units, off the Virginia and Carolina coasts and in the Caribbean until 1960. 

 On 22 October 1962 she departed Norfolk on what was to be a month-long training cruise in the Caribbean, but the formation of the Cuban-Missile crisis blockade force altered the cruise plans. On 3 December, she returned to Norfolk and from then into 1967 she maintained her schedule of exercises with the Marine Reconnaissance, UDT, and SEAL personnel. On 15 September 1967, her last two years of active service, she operated out of Key West as a unit of SubDiv 121. Reclassified LPSS-315 in January 1969, Sea lion was ordered inactivated the following summer; and, in September, she proceeded to Philadelphia where she was decommissioned and placed in the inactive fleet on 20 February 1970.