USS Seawolf (SSN-575) was the third ship of the United States Navy to be named for the seawolf, the second nuclear submarine, and the only US submarine built with a liquid metal cooled (sodium), beryllium-moderated nuclear reactor, the S2G. Her overall design (known as SCB 64A) was a variant of , but with numerous detail changes, such as a conning tower, stepped sail, and the BQR-4 passive sonar mounted in the top portion of the bow instead of further below. This sonar arrangement resulted in an unusual bow shape above the water for a U.S. submarine. Originally laid down in 1953, her distinctive reactor was later replaced with a standard pressurized water reactor, the replacement process lasting from 12 December 1958 to 30 September 1960.

Comparison to Nautilus

Seawolf was the same basic "double hull" twin-screw submarine design as her predecessor , but her propulsion system was more technologically advanced. The Submarine Intermediate Reactor (SIR) nuclear plant was designed by General Electric's Knolls Atomic Power Laboratory and prototyped in West Milton, New York. The prototype plant was eventually designated S1G and Seawolfs plant as S2G.

The Atomic Energy Commission historians' account of the sodium-cooled reactor experience was:

The S2G reactor was replaced with a pressurized water reactor similar to Nautilus and designated S2Wa, the replacement process lasting from 12 December 1958 to 30 September 1960.

Although fully armed, Seawolf, like the first nuclear submarine, Nautilus, was primarily an experimental vessel. Seawolf was originally thought of publicly as a hunter-killer submarine, but in fact was intended to be a one-off test platform for the SIR (aka S2G) LMFR reactor and future sonar platforms. Her future uses, after the reactor plant was replaced with a light water system, included covert operations in foreign waters, for which she was converted January 1971 – June 1973. wife of New York Congressman W. Sterling Cole, and commissioned on 30 March 1957.

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Like all of the original nuclear subs, the project manager at Electric Boat was the general manager of the company, Bill Jones. During the parallel construction of the first nuclear submarines, the Navy, the Atomic Energy Commission, its independent labs, and the shipyard all worked together to learn together.

For the yard, the Power Plant Project manager was a separate function on these original nuclear subs. Dennis B. Boykin III would lead EB's power plant installation, and return to the project two years later for the reactor conversion. His counterpart at the Office of Naval Reactors, Gardner Brown, did the same.

Lieutenant James Earl "Jimmy" Carter, the only US President to qualify in submarines, was to be her Engineering Officer, but had resigned his commission upon the death of his father in 1953.

1957–1959

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Seawolf departed New London, Connecticut, on 2 April for her shakedown cruise off Bermuda and returned on 8 May. Between 16 May and 5 August, she made two voyages to Key West and participated in intensive training exercises. On 3 September, she steamed across the North Atlantic to participate in NATO exercises. The submarine surfaced off Newport, Rhode Island, on 25 September after cruising nonstop. The next day, President of the United States Dwight D. Eisenhower embarked and was taken for a short cruise onboard her.

Seawolf cruised to the Caribbean Sea for an exercise in November. In December, she began an availability period that lasted until 6 February 1958. She then participated in exercises along the east coast until early August.

Seawolf submerged on 7 August and did not surface again until 6 October. During this period, she logged over . She received the Navy Unit Commendation

1960–1966

Seawolf began a three-week period of independent operations on 25 October, and returned to fleet operations in November and December. On 9 January 1961, Seawolf sailed to San Juan, Puerto Rico, to participate in local operations. On 25 January, she was ordered to locate and track the Portuguese passenger liner Santa Maria which had been seized by pirates two days earlier. The submarine made contact with the liner off the coast of Brazil on 1 February. After Santa Maria surrendered in Recife, the submarine returned to San Juan and continued east coast operations.

On 7 July, Seawolf began a two-month oceanographic voyage which took her to Portsmouth, England, before returning the vessel to New London on 19 September 1961.

In 1963, Seawolf participated in the search for the lost submarine and in various local and fleet operations until April 1964. On 28 April, Seawolf stood out of New London en route to the Mediterranean Sea and a -month deployment with the Sixth Fleet. During the period, she operated with aircraft carrier , guided missile cruiser , and guided missile destroyer as a part of the world's first nuclear task force. More local East Coast exercises followed until 5 May 1965. On that date, the submarine entered the Portsmouth Naval Shipyard for refueling and an extensive overhaul bringing her up to the SUBSAFE standard put in place after the loss of Thresher. This overhaul lasted until September 1966.

1967–1973

Seawolf sailed from Portsmouth, New Hampshire, on 24 August 1967 for New London, Connecticut, which was again her home port. The following month, she sailed to the Caribbean Sea for refresher training and weapons trials. She had to have a propeller replaced at Charleston, South Carolina, in early October and then conducted sea trials in the Bahama Islands for the remainder of the month. The end of the year 1967 found her back at her home port.

Seawolf was operating from that port when she grounded off the coast of Maine on 30 January 1968, badly crushing her stern. She was towed back to New London, Connecticut, for repairs and did not put to sea again until 20 March 1969, when she began sea trials. The submarine was in the Caribbean Sea during June and July conducting underwater sound and weapons systems tests. Seawolf was deployed with the Sixth Fleet from 29 September to 21 December 1969.

Seawolf operated along the East Coast until 9 November 1970 when her home port was changed to Vallejo, California, and she sailed for the West Coast. The submarine transited the Panama Canal on 17 November and changed operational control to Submarine Force, Pacific Fleet. In the Pacific, Seawolf would serve as a "spy submarine", trailing other submarines, retrieving test weapons from the seabed, and tapping Soviet submarine communications cables.