Australia:
E-class submarine HMAS AE1 at sea in 1914.
HMAS
AE1 with HMAS
Australia and HMAS
Yarra at a rendezvous off Rossel Island in September 1914, photographed from the bridge of HMAS
Encounter.
At 07:00 on 14 September,
AE1 departed
Blanche Bay, Rabaul, to patrol off
Cape Gazelle with
HMAS Parramatta. When she had not returned by 20:00, several ships were dispatched to search for her. No trace of the submarine was found, and she was listed as lost with all hands. The disappearance was Australia's first major loss of World War I
After the discovery of the submarine in December 2017, Rear Admiral Peter Briggs, retired, said the likely cause of its loss was a diving accident. He added:
The submarine appears to have struck the bottom with sufficient force to dislodge the fin from its footing, forcing it to hinge forward on its leading edge, impacting the casing.
As of April 2018, the best-supported theory for the submarine's loss was that it went below its
crush depth due to a mechanical failure. Later that year, a team of researchers headed by the
National Maritime Museum director Kevin Sumption concluded their investigation into the sinking of
AE1. They concluded that a ventilation valve, which was likely open to make the tropical conditions a little more bearable while the submarine was cruising on the surface near the
Duke of York Islands, was insecure when the submarine dived, causing a flood of the submarine's engine room and total loss of control of the
AE1. The submarine subsequently sank below 100 metres and imploded, killing everyone on board instantly