"Sea Owl" was converted to a Fleet Snorkel submarine in the Philadelphia Navy Yard from April to August 1951 and, for the next year, she participated in Atlantic Fleet exercises in the Caribbean area. Early in 1953, the submarine entered Charleston Naval Shipyard in South Carolina for overhaul and, upon completion, sailed to New London and then to the Caribbean as part of operation "Springboard." After returning to New London in March, she departed for her first tour of duty with the 6th Fleet in the Mediterranean, participating in fleet exercises and in Operation "Keystone" and visiting France, Italy, Spain, Greece, and Turkey in a three-month tour.