During World War II, "Caiman" sailed from Pearl Harbor on her first war patrol 13 November 1944. Pausing at Saipan to put ashore her severely ill commanding officer and embark his relief, the submarine pushed on to the South China Sea, where she combined offensive patrol with lifeguard duty as a part of air-sea rescue operations to save aviators downed in air strikes on enemy-held territory. Aggressive American submarine and naval air attack had already greatly reduced the Japanese merchant fleet; hence "Caiman" made no contacts on this patrol, from which she returned to Fremantle, Australia, on 22 January 1945 to refit.