Australia's first submarine was most likely lost during an underwater operation off the coast of Papua New Guinea as it returned to Rabaul.
A report from the Find AE1 Limited expedition that discovered the wreck of HMAS AE1 near the Duke of York Islands in December was attempting to piece together one of Australia's oldest naval mysteries.
Defence Minister Marise Payne said the images collected showed the World War I submarine's guardrails were stowed and hatches appeared to be shut.
"The report indicates that the AE1 was probably submerged or diving while she was returning to Rabaul, after a patrol looking for enemy activity around the Duke of York Islands, when tragedy struck," said Ms Payne.
"Through the tireless efforts of many, we have discovered the final resting place of the 35 souls who gave everything in service to the Allied cause."
The team of maritime surveyors, marine archaeologists and naval historians scoured the search area with a multi-beam echo sounder and side-scan technology in an underwater drone flying 40 metres above the sea bed on pre-programmed 20-hour missions.
The data collected was analysed and a three-dimensional rendering of the underwater environment was produced before dropping a camera to confirm the find.
The search for HMAS AE1 was supported by the Royal Australian Navy, Silentworld Foundation, the Australian National Maritime Museum, the Submarine Institute of Australia, Fugro Survey, and the Government of Papua New Guinea.
