バラバク海峡
"Sculpin"s fourth war patrol, from 29 May – 17 June, was in the South China Sea. On 8 June, she was unsuccessful in an attack on a cargo ship, again due to torpedo malfunction. A vigorous depth charge attack kept "Sculpin" down while the cargo ship escaped. On 13 June, near Balabac Strait, she torpedoed a cargo ship which returned fire with her deck gun and commenced to limp away. Turning on two accompanying tankers astern of the cargo ship, "Sculpin" made an attack but was forced to dive to prevent being rammed by one of the tankers. Surfacing at dusk, "Sculpin" pursued the cargo ship, but was again driven away by accurate gunfire from the maru. She shifted her attack to a tanker, leaving the ship listing and making heavy smoke. However, no sinking was confirmed. Off Cape Varella, Indochina, early on the morning of 19 June, she torpedoed a cargo ship, making a hit forward of the stack. A heavy secondary explosion was heard, and the damaged vessel was last seen headed for the shore to beach, smoke pouring from her forward hatch. "Sculpin" returned to Australia on 17 July. She moved to Brisbane, under Ralph Waldo Christie (part of Admiral Arthur S. Carpender's 7th Fleet, and ultimately General Douglas MacArthur's South West Pacific Area command), along with the rest of Submarine Squadron Two (SubRon 2), in August.