A mission to uncover the secrets of a century-old Australian Navy submarine which was mysteriously lost at sea along with its entire crew has taken place off Papua New Guinea.

The HMAS AE1, the first-ever submarine belonging to the Royal Australian Navy, went missing in September 1914 during the early stages of World War I.

Commanded by Lieutenant Thomas Besant, the vessel left the Papua New Guinea township of Rabaul on the morning of September 14, 1914. The patrol was the submarine’s last, however, and the 35 crew onboard were never seen again.

Now a joint US and Australian expedition has surveyed the area in an effort to pull further clues from the deep, and figure out what happened in the moments after the submarine was disappeared.

Undertaken with the help of Microsoft co-founder Paul Allen, who donated his research ship Petrel, April’s exploratory operation involved an underwater drone used to film and inspect the wreck using high-definition cameras. The incredible images show the remains of the sub’s bridge, control room and ceramic toilet pots.

Rusted torpedo tubes, once primed for war, are seen teeming with moss and plankton. According to the Australian Navy, the AE1 was accompanied by the HMAS Parramatta destroyer when it went missing in poor weather.

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“Parramatta reported that AE1 was obscured by the haze for some time, as was the nearest land. Given these conditions, Parramatta’s Commanding Officer… considered it advisable not to lose sight of the submarine for too long,” a naval account states.

“At 3.20pm the submarine was lost sight of and Parramatta altered course and steamed in the direction she was last seen. No sign of AE1 was found and it was considered that she must have steamed back to harbour without informing Parramatta,” it adds. The submarine lay undiscovered on the seafloor near the Duke of York Islands until December 2017, when a search crew came across the sunken wreck 300 meters underwater.

The images collected could provide answers to the submarine’s mysterious loss, which over the years yielded much speculation, including that it was sunk by an enemy German submarine or struck by a fellow navy vessel. Data will also be provided to the Australian National Maritime Museum.

“These incredible images and the new information they provide will help the museum tell the story of AE1 and its brave crew, and ensure their service and sacrifice are remember by future generations,” said Kevin Sumption, Australian National Maritime Museum Director.

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