Greenfish during her 2-month cruise included Manila, Singapore, Rangoon, where she was the first submarine ever to visit and was inspected by Burmese Prime Minister U Nu, and Hong Kong. After further exercises off Okinawa and Yokosuka, Greenfish returned to Pearl Harbor 13 March 1956. The following 5 years fell into a pattern for Greenfish—local operations out of Pearl Harbor, special operations, exercises along the American coast, and periodic overhauls. Greenfish entered Pearl Harbor Shipyard 15 December 1960 for a FRAM (Fleet Rehabilitation and Modernization) overhaul and extensive conversion to a GUPPY III class ship. This included cutting Greenfish in half and adding a section of hull to permit more batteries and other equipment. Conversion completed, Greenfish departed 28 July 1961 for shakedown, operations at Pearl Harbor, and in December sailed to serve with the 7th Fleet. In addition to special operations, the submarine participated in various fleet and ASW exercises and visited several ports, including Hong Kong, Manila, and Okinawa. Returning to Pearl Harbor June 1962, Greenfish engaged in local operations until October, when the Cuban Missile Crisis sent her to Japan to strengthen the 7th Fleet. Upon return to Hawaii December 1962, she underwent a brief overhaul and then resumed her peace time schedule of local and special operations interspersed with training exercises. Based at Pearl Harbor, she participated in various ASW exercises while maintaining the high tempo of training and readiness for her crew. From 30 March 1964 to 4 September she underwent overhaul; and, after a cruise to the Pacific Coast and back, Greenfish departed for the Far East 27 January 1965. She arrived Japan early in February and during the next 4 months operated with the 7th Fleet in waters from Japan to the Philippines. She returned to Pearl Harbor 1 August, continued type training into 1966, and deployed once again to the Western Pacific 1 February 1966. She completed her duty with the 7th Fleet 1 July and returned to Hawaii later that month to resume readiness exercises out of Pearl Harbor. Into 1967 she continued to serve in the Pacific Fleet's submarine force. In 1970 she underwent a yard overhaul at Hunters Point Naval Shipyard, San Francisco, CA. She then underwent weapons alignment in Bangor, WA. Greenfish Transited the Panama Canal and proceeded to Sub base New London. She made a Med cruise and North Atlantic cruise in 1971 and a springboard exercise