バラバク海峡
"Barbel" departed Fremantle submarine base, Western Australia, on 5 January 1945 for the South China Sea on her fourth patrol, Lt. Cdr. Conde Leroy Raguet in command. Late in January she was ordered to form a "wolfpack" with and and patrol the western approaches to Balabac Strait and the southern entrance to Palawan Passage. On 3 February, "Barbel" sent a message reporting that she had been attacked three times by enemy aircraft dropping depth charges and would transmit further information on the following night.