It was one of the most daring raids of the second world war. On the night of May 31, 1942, three Japanese midget submarines sneaked into Sydney harbour, bringing the war to the heart of Australia's largest city. Their mission was to sink the USS Chicago, a big American warship anchored off the Garden Island naval base.
But the attack did not go according to plan. The first midget sub became trapped in an underwater boom net and blew up. The second was destroyed by depth charges, its two officers shooting themselves rather than risk capture.
Only the third, codenamed M24, was able to get close enough to the naval base to fire off two torpedoes.
Instead of hitting the Chicago, however, the torpedoes slammed into an Australian ship, HMAS Kuttabul, killing 21 sailors and marines. The M24 was never heard of again - until now.
Over the years there were various theories about what happened to the sub: that it sank inside the harbour; or made a rendezvous in the open ocean with its 'mother' submarine; or even that the two-man crew came ashore, walked through the streets of Sydney and were picked up by a Japanese dinghy.
A team of divers, historians and filmmakers now say they have evidence that the sub made it out of the harbour and then turned north, perhaps as a way of distracting Australian forces from its parent fleet to the south. The team believes that the sub cruised along the coast for about 14 nautical miles before running out of power, or being deliberately scuttled, near Scotland Island, at the mouth of the Hawkesbury River.
