The patron of a long-running effort to find the wreck of the Australian World War II warship HMAS Sydney, claims that the ship has been found, and needs to be verified as soon as possible.

The Sydney sank with 645 crew on board in November 1941, after a battle against the German raider Kormoran off the coast of Western Australia.

The ship's wreck has never been found, but now a team of amateur researchers is claiming to have located it in 150 metres of water off Dirk Hartog Island near Carnarvon.

Former deputy prime minister Tim Fischer, a patron of the Finding Sydney Foundation, says despite a number of false leads in the past, this one seems to have substance.

"This is seemingly a welcome breakthrough after all these years - over six decades - and if it proves up to detailed analysis [the families] will be absolutely delighted," he said.

"[There will be] closure for many families living in Sydney and Melbourne and right around Australia, who lost loved ones and members of their family on the HMAS Sydney when it sank."

The Foundation's Bob Trotter says the claim is exciting but needs to be verified.

"If they're right we'd be the first to say well done," he said.

Map: Carnarvon 6701

HMAS Sydney Details And History