USS Tusk (SS-426), a , was the only ship of the United States Navy to be named for the tusk, an alternate name for the cusk, a large edible saltwater fish related to the cod. Her keel was laid down on 23 August 1943 at Philadelphia by the Cramp Shipbuilding Company. She was launched on 8 July 1945 sponsored by Mrs. Carolyn Park Mills, and commissioned on 11 April 1946. Tusk and are erroneously listed with the Tench class in some sources, as their hull numbers are in the sequence assigned to that class. Shakedown and GUPPY Conversion Tusk completed her shakedown cruise in the southern Atlantic with a round of goodwill visits to Latin American ports. She called at Rio de Janeiro and Bahia in Brazil, Curaçao in the Netherlands West Indies, and at Colón in the Panama Canal Zone before returning to New London, Connecticut, in June. For the next year, she conducted operations along the East Coast between New London and Wilmington, North Carolina. During the first month of 1947, Tusk participated in a fleet tactical exercise in the Central Atlantic. A three-month overhaul at Philadelphia, followed by oceanographic work along the Atlantic shelf in conjunction with Columbia University and the Woods Hole Oceanographic Institution occupied her until October 1947 when she entered the Portsmouth Naval Shipyard for a Greater Underwater Propulsive Power Program (GUPPY) conversion. Over the next seven months, Tusk received extensive modifications to improve her submerged performance characteristics. Four "greater capacity" batteries replaced her old larger ones. Her hull became more streamlined—the anchors were recessed into the hull and the propeller guards were removed—to improve her overall hydrodynamic design for underwater operations. Her sail was streamlined and enlarged to house the snorkel, a device added to allow her to operate on diesel power at periscope depth and to recharge her batteries while running submerged. All of these changes helped to convert Tusk from simply a submersible surface ship into a truer submarine. They increased her submerged range; and, though she lost about two knots in surface speed, her submerged speed increased from just under to about . The newly converted submarine returned to active duty early in the summer of 1948. She conducted her shakedown training and made a simulated war patrol to the Panama Canal Zone in June and July. She returned to the United States in August and visited the United States