She held training exercises and torpedo-tube testing off the coast of Connecticut and Rhode Island until 22 October.

Sennet refitted at Saipan from 31 January to 7 February, when she began her second war patrol off southern Honshū, Japan.

Three days later, the submarine attacked the minelayer Nariu with an offset spread of torpedoes from her stern tubes, then went deep to 200 feet (60 m).

The submarine surfaced an hour later and saw a large oil slick and approximately 40 Japanese clinging to debris but no trace of the Nariu which had sunk.

When the war ended in the Pacific, Sennet was assigned to the Atlantic Fleet and operated from New London, Conn.

The ship conducted training for submarine and antisubmarine personnel at Key West and Guantanamo Bay, Cuba.

In 1951, Sennet was converted to a Fleet Snorkel submarine at the Philadelphia Naval Shipyard and returned to her homeport.

From her return on 30 January 1955 until 1 August 1959, the submarine conducted training, local, and fleet operations with her squadron.