AE1 mystery continues: Navy search for Australia's first submarine fails to find conclusive evidence

The Chief of Navy says a search for Australia's first submarine, missing off Papua New Guinea for a century, has not yielded anything conclusive.

The minehunter HMAS Yarra spent four days combing the waters near the Duke of York Islands looking for the AE1.

Vice Admiral Tim Barrett said the search had not yielded any conclusive evidence of the submarine's final resting place.

"What was found over the last couple of days has not led me to say that we have found AE1," Vice Admiral Barrett said.

The disappearance of the AE1 and its 35 crew is one of the enduring mysteries of Australian maritime history.

It vanished without a trace 100 years ago this week while patrolling the waters off Rabaul, shortly after Australian forces took control of what was then German-administered New Guinea.

Vice Admiral Barrett said HMAS Yarra found several objects, one which was larger than the others, that had the characteristics of a submarine.

But he said the sonar imagery that had been collected would undergo closer analysis.

"There is an object that is in the water, in the area, that is about the same size, but there are other objects that are in the water of slightly different sizes but of the same sort of characteristics," he said.

Vice Admiral Barrett said it was a difficult search with the seafloor in the area strewn with large boulders and rapid changes in depth.

The Navy has made a number of attempts at locating the AE1. This time it was investigating local historical accounts, including one from Mioko Islanders who spoke of a "monster" that approached a nearby reef then moved away and disappeared.

Relatives of AE1 crewmembers boarded HMAS Yarra off Rabaul on Wednesday to take part in a commemoration service to mark the 100th anniversary of the disappearance.

A wreath-laying service was held on the back of the HMAS Yarra to remember those who died.

On board was Robyn Rosenstrauss, whose grandmother's brother, James Fettes, served on the AE1.

She said it was an emotional experience and she could only hope that his death was a quick one.

David Messenger, whose grandfather's brother John served on AE1, said he hoped finding the submarine would finally bring some answers to the mystery.

"No-one knows what happened to it [so] it'd be nice to have an answer of what exactly did happen," he said.

"I would like research done to see why it sunk, but that'd be it. It's a war grave."

AE1 had been dispatched to seize German colony

The AE1 disappeared while on patrol with the destroyer HMAS Parramatta.

It was part of a flotilla dispatched to seize New Guinea after the outbreak of World War I.

The disappearance marred an otherwise successful mission, including the surrender of Rabaul by German forces a few days before.

Rabaul, on the northern tip of the island of New Britain, was the site of fierce fighting during World War II and became Japan's key naval base for the south-western Pacific from 1942.

The town's harbour, surrounded by active volcanoes, is popular with divers due to the easy access to war wrecks.

The AE1's sister ship AE2 survived the New Guinea campaign but was sunk by a Turkish torpedo boat in April 1915 after disrupting enemy ships bound for Gallipoli.