After escaping a strafing attack by a Japanese fighter on 7 December, she made contact and commenced tracking two cargo ships with two escorts on the morning of 13 December, south of Kyūshū. That night, she fired a spread of four torpedoes at the two freighters. Two solid explosions were heard, including an internal secondary explosion. "Sailfish" heard "Totai Maru" () break up and sink as the destroyers made a vigorous but inaccurate depth charge attack. When "Sailfish" caught up with the other freighter she was dead in the water, but covered by a screen of five destroyers. Rather than face suicidal odds, the submarine quietly left the area. On the night of 20 December, she intercepted an enemy hospital ship, which she left unmolested.