HMAS AE1 was lost off Rabaul on September 14, 1914 and the fate of its 35 crew members had been "one of the significant mysteries of Australian military history", according to Defence.

It was the first loss for the Royal Australian Navy and the first Allied submarine loss in World War I, the crew a mix of Brits, Australians and New Zealanders.

Canberra academic Dr Kathryn Spurling in 2014 self-published The Mystery of AE1, Australia's Lost Submarine and Crew, working closely with the descendents of the crew to tell their story.

Dr Spurling said the submarine was lost "just 40 days after the nation was committed to battle in World War I", making it a significant but largely overlooked tragedy.

"It was the first Australian unit lost in World War 1, a long time before Gallipoli," she said.

"The army, because of the numbers involved, really took over military history. The navy was forgotten."

The news this week that the submarine had been found more than a century after it went missing had hit them all hard. She had written in her book that Australia had for too long neglected the lost crew and their families.

"I was just overwhelmed," Dr Spurling said, from her Chifley home.

"This has been going on for 103 years. I got to know a lot of the relatives and descendants, who are a very active lot, over many years when I was doing the research.

"You can't help but see the pain in these people's eyes. It's a case of we made a lot of fuss about soldiers being buried but when you're in the navy, you get buried at sea or you go down with the ship and that's the end of it.

"So, the fact they've been found, it's amazing. I've had a lot of emails from relatives today saying it's very emotional and overwhelming for them and that they wish their grandparents or parents were alive because they were brothers, sisters, children [of the dead]."

A new expedition to find the submarine started last week and the search vessel Furgro Equator this week located the submarine in more than 300 metres of water.
Defence said the Australian Government would work closely with the Papua New Guinean Government "to consider a lasting commemoration and recognition of the crew of AE1 and to preserve the site".

Dr Spurling said the relatives did not want the submarine brought to the surface.

"The remains are entombed and that means it's a war grave," she said.

"They don't want anything disturbed. They think it is best left as it is. Perhaps a buoy at the surface with a plaque commemorating the site."

In her book, Dr Spurling, who has a PhD in military history, outlined various theories about what had happened to the submarine but none that she could confirm.

Those theories included that an enemy destroyer had run over it, but there was no sign of an oil slick or debris from a damaged hull in the area. It may have dived to escape a German vessel and suffered a catastrophic mechanical failure. The submarine had no deck gun and it's "only defence was to dive". There was also speculation it had hit a mine or a reef or run into mechanical problems during a practice dive.

"It is believed the only consolation was that the water in the vicinity of where the submarine was last seen was very deep and the hull would have been unable to withstand the pressure very long - 'death would be mercifully sudden' - a small consolation," she wrote in her book.

Happy that her book was now in print, Dr Spurling said she was greeted with a "very patronising" attitude from potential publishers when she had been trying to sell the history of the doomed submarine.

"They just said it wasn't a book that would have a readership and I found that amazing, really," she said.

The book's cover features a painting by Canberra artist Margaret Hadfield, who joined Dr Spurling on Friday in remembering the lost men and their descendants.

The successful search was jointly funded by the Australian Government, the Silentworld Foundation, the Australian National Maritime Museum and Find AE1 Ltd; usingFugro Survey's vessel and search technology.

Defence said the search 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".