When the submarine raised her periscope, a destroyer passed over the conning tower and attacked with depth charges causing minor damage.

On the night of 13 March, Sunfish torpedoed and sunk the 3,262-ton Kosei Maru, a cargo ship in the approaches to Takarajima (Toro Shima in DANFS) in 29°04′N 129°17′E / 29.067°N 129.283°E / 29.067; 129.283.

In the early-morning hours of 4 September, Sunfish dodged between lighted sampans to attack a 10-ship convoy, sinking the Kozon Maru, which also exploded.

When she returned to Pearl Harbor on 7 March, she was routed onward to San Francisco for an overhaul, which was completed in early June.

Following her overhaul, the Sunfish returned to Pearl Harbor and departed for her seventh war patrol on 22 June in the Kuril Islands area.

On 10 September she intercepted a convoy coming out of Tsushima Strait, sinking Chihaya Maru and damaging several other targets.

On the night of 13 September, the Sunfish attacked another convoy sinking the Etashima Maru with damage claimed to other targets, including one ship left with her decks awash.

Sunfish returned to the Yellow Sea on 23 October as part of a "wolf pack" that included Peto (SS-265) and Spadefish (SS-411).

The patrol ended at Majuro, Marshall Islands, on 19 December 1944, with the wolfpack having sunk a total of 59,000 tons of Japanese shipping.

The submarine carried out a daylight attack on 16 April, sinking the transport Manryu Maru and the frigate Coast Defense Vessel No.

Sunfish was in the Mare Island Naval Shipyard from 7 May to 31 July for an overhaul and returned to Pearl Harbor on 9 August.

Sunfish remained out of commission, serving as a classroom for naval reserve units until she was struck from the Navy List on 1 May 1960.