Experts are hoping the discovery of the HMAS AE1 in deep waters off Papua New Guinea will help shed light on why Australia's first submarine disappeared more than a century ago.
The wreck and the remains of her three officers and 32 sailors, who vanished on September 14 in 1914, was located off the coast of PNG's Duke of York Island on Wednesday.
A day after it was involved in the occupation of German New Guinea and the surrender of Rabaul, the AE1 became the first Allied submarine to be lost in World War I and the Royal Australian Navy's first casualty.
What happened after it vanished off the township of Rabaul had been one of Australia's biggest military mysteries.
But Wednesday's discovery, in more than 300 metres of water, could help experts determine how it sank, with a diving accident believed to be the likely cause.
