Remains of a Japanese mini submarine may have been found north of Sydney Harbour in 20 meters of water.  The sub, known as M24, was one of three which attacked Sydney on May 31, 1942.  The other two subs were recovered from the bottom of the harbour as the crews had killed themselves after failing to escape.  The location of the third sub had been unknown.

  Herald Sun article...

The Wilkins-Ellsworth Polar Expedition of 1931 makes a fascinating story.  Far before its time, the idea was to navigate underwater from Spitsbergen Norway into the Bering Strait, right under the Arctic ice cap.  This expedition was organized by an Australian explorer, involved a submarine named Nautilus and, just to jump ahead, did not prove successful.  In fact, this Nautilus now rests in 1100 feet of water off Bergen, Norway...

Obscure clue leads Melbourne shipwreck hunters to intact 1929 wreck of a passenger ship.
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