Operating out of the Submarine Base, New London, Connecticut, she conducted training missions in the North Atlantic, and, in November 1946, made a cruise above the Arctic Circle.

In January 1947, the submarine entered the Portsmouth Naval Shipyard for extensive modifications and thereafter spent about a year undergoing a Greater Underwater Propulsion Power Program (GUPPY) conversion during which her hull and sail were streamlined and additional batteries and a snorkel were installed to increase her submerged speed endurance, and maneuverability.

On 2 September 1969, following another 25 months of operations along the US east coast and in the West Indies, she embarked upon her last deployment from Charleston in European waters during which she participated in another NATO exercise with units of the British, Canadian, and Dutch navies.

According to the memo, General Steakley “briefed the committee on a sensitive DOD project known as FRONTLET 615,” which is identified in a handwritten note on the original memorandum as “submarine within U.A.R.

In February 1997, a senior member of the crew of the Amberjack told Liberty survivor James Ennes that he had watched the attack through the periscope and took pictures.

On 9 July 1970, Amberjack arrived in her new home port, Key West, Florida, her base for the remainder of her service in the United States Navy.

On 17 October 1973, Amberjack was decommissioned at Key West, her name was struck from the Naval Vessel Register, was transferred to the Brazilian Navy, and was commissioned as Ceará (S-14).