Arriving on 9 April, "Seal" departed again on 12 May and worked her way through the Malay Archipelago, the Celebes Sea, and the Sulu Sea to her patrol area off the Indochina coast. During the early morning hours of 28 May, she entered the South China Sea, and that night, she fired on and sank 1,946-ton "Tatsufuku Maru". On 7 June, while off Cam Ranh Bay, she attacked an eight-ship convoy and underwent a seven-hour depth charging by surface ships and aircraft. From 15–17 June, heavy seas and high winds hampered hunting, and on 18 June, "a healthy stream of air bubbles" was discovered "issuing from the starboard side..." On 19 June, she left the area and headed for Balabac Strait. On 23 June, she moved into Makassar Strait, and on 4 July, she reached Fremantle.