Jaluit Atoll
After a major overhaul at Mare Island, "Porpoise" departed Pearl Harbor for her fourth war patrol - from 30 November 1942 – 15 January 1943 - off the coast of Honshū, Japan. On 1 January 1943, she sank "Renzan Maru", then set course for Midway where she completed the patrol. Her fifth war patrol - from 6 February–15 April - off Jaluit Atoll, was highlighted by the sinking of "Koa Maru" on 4 April.