The Gudgeon was commissioned in 1941 and was a submarine of the Gato Class which was an improved version of the Tambor Class of which Thresher was an example. She was armed with one 3-inch, 50 caliber gun and two 20mm Oerlikons. She had ten 21-inch torpedo tubes, six bow and four stern. This class had two engine rooms instead of the single engine room of the Tambor Class. On 7 December she was moored in South-East Loch west of the CinCPAC headquarters.