Balabac Strait
"Salmon" departed from Fremantle on 21 July for her fourth war patrol in the South China Sea-Sulu Sea area. Sailing via Lombok Strait and Makassar Strait, the Sibutu Passage, and the Balabac Strait, she stationed herself between North Borneo and Palawan, Philippine Islands. During this patrol, "Salmon" was unable to gain a favorable position for successful attack, but made numerous sightings and reports of shipping movements to sister subs in the vicinity. She returned to Fremantle on 8 September.