On 24 August, south of Formosa, "Sailfish" made radar contact with an enemy convoy consisting of four cargo ships escorted by two small patrol craft. Moving into firing position, "Sailfish" fired a salvo of four torpedoes, scoring two hits. The cargo ship "Toan Maru" () was enveloped in a cloud of smoke and shortly afterwards broke in two and sank. Surfacing after escaping a depth charge attack, "Sailfish" closed on a second cargo ship of the convoy, scoring two hits out of four torpedoes fired. The submarine's crew felt the cargo ship either had been sunk or badly damaged, but the sinking was not confirmed by JANAC postwar. "Sailfish" terminated her 11th patrol at Midway on 6 September; her wartime credit was four ships for , a total reduced to just one of ("Toan Maru") postwar.