More than 80 years on from a dark moment in Australia's military history, researchers believe they might have tracked down a Japanese submarine involved in a World War II attack.
A KD7 class submarine I-178 that torpedoed a Allied ship might be wrecked off the coast of Coffs Harbour with researchers pointing to "strong evidence".
Heritage NSW released the new study on the 83rd anniversary of the Japanese attack on the Sydney Harbour, where three submarines entered in 1942.
Australian air force planes bombed an unidentified ship about 104km southwest of Coffs Harbour, while eye witnesses saw an oil slick the day after off Nambucca Heads.
Heritage NSW assessments director Tim Smith said the study recommended a seabed survey of the area to locate the submarine.
"The detailed research shines new light on this dark period of our history and adds weight to the hypothesis that the long lost I-178 lies on the ocean floor off the coast of Coffs Harbour, while also strongly rejecting one theory that it sank near Vanuatu," he said.
"Interestingly, we don't know why this particular submarine - which should have been capable of staying underwater for long periods - was caught on the surface twice in a short space of time."
The study suggests it may have had battery or operational problems from a previous attack which prevented it from submerging.
The 105-metre Japanese KD7 class submarine I-178 and its 89 crew were declared lost in 1943 and have never been located.
The last signal it sent back to headquarters was on June 18, 1943.
Axis naval forces killed 214 people and sunk 23 ships in NSW waters in attacks between 1941 and 1944.
Three midget submarines entered Sydney Harbour on May 31, 1942, but two were detected and attacked before launching their own offensives.
The third submarine was discovered off Sydney's northern beaches in 2006.
