classification symbol SSR-481 on 20 January 1948, Requin began modification to the MIGRAINE II Radar Picket configuration at the Portsmouth Naval Shipyard in Kittery, Maine. In December, she departed the shipyard after completing trials with new radar equipment. She reported to New London, Connecticut for duty with Submarine Squadron 8. In May 1949, she sailed east for her first deployment with the Sixth Fleet. Arriving at Gibraltar on 14 May, she operated in the Mediterranean Sea until 30 June. Soon after returning to New London, Requin was transferred to Norfolk, Virginia for duty with SubRon 6. Into the spring of 1950, she operated in the western Atlantic, ranging from Nova Scotia to the West Indies. Overhaul occupied most of the summer, and with the end of the year, she prepared for another Sixth Fleet tour. In the Mediterranean from mid-January to mid-May 1951, she resumed operations off the East Coast and in the Caribbean Sea on her return. In August 1952, she was back in European waters. During September, she visited the United Kingdom; then, in October, the submarine transited the Strait of Gibraltar for her regular Sixth Fleet duty. In 1953, she maintained her schedule of Second and Sixth Fleet operations, but at the end of the year put into Philadelphia, Pennsylvania, for an extensive modernization overhaul that among other changes removed her last anti-aircraft cannon. On 2 May 1955, she sailed for her fifth Mediterranean deployment. Detached at the end of July, she returned to Norfolk. She remained on the East Coast, with cruises to the Caribbean, until November 1957, when she resumed duty with the Sixth Fleet. Second conversion From June through August 1959, the Charleston Navy Yard in South Carolina removed all of Requins radar equipment and improved her streamlining. Upon her conversion to Fleet Snorkel configuration, she was given hull classification symbol SS-481 on 15 August 1959, and rejoined SubRon 6 in Norfolk for operations as a normal attack submarine, a role she retained until her decommissioning. Requin conducted local operations off the East Coast and in the Caribbean Sea. In the summer of 1961, Requin served as a target for Task Group Alpha led by USS Saratoga CVA 60. Requin conducted a periscope approach on Saratoga and launched a simulated torpedo attack. Then a helicopter dropped an exercise torpedo on Requin, which hit forward and made several re-attacks bouncing down the port side of