On September 14, 1914, the Royal Australian Navy submarine AE1 went missing, triggering one of the country's greatest maritime mysteries.

The sub, one of the Royal Australian Navy's first, vanished while on patrol in waters off the coast of Papua New Guinea in the opening days of World War I with 35 Australian, New Zealand and British crew on board. There was no distress call, and there were no witnesses.

The location of HMAS AE1 remained a mystery for more than a century until it was discovered in 300 metres of water off the coast of Papua New Guinea's Duke of York Island.

In 2017, after years of fruitless searches, a camera sent deep into the water off Duke of York Island this confirmed the wreck was the lost submarine.

Analysis of the wreck by naval experts determined that a vital valve left open when the submarine dived caused water to flood the engine room.

Source: Royal Australian Navy