Captain Cook's Endeavour Possibly Found Off America's East Coast

Australian and U.S. archaeologists believe they may have found Captain James Cook's HMB Endeavour.

It could take four months to test wood taken from a wreck found at the bottom of a harbour on America's east coast.

A 25-year-long archaeological study of transport ships deliberately sunk by the British in Newport Harbour, Rhode Island, in 1778 during the American War of Independence has led to a wreck that fits the dimensions of the Endeavour.

"There's still a lot of work ahead, but it is an exciting day," Australian National Maritime Museum director Kevin Sumption told AAP.

The results of the study were announced at a press conference on Friday held by Dr Kathy Abbass, founder of the Rhode Island Marine Archaeology Project.

Captain James Cook. Image: Getty Images.

The Endeavour, through its lifetime, was used for different purposes.

After Captain Cook took it on his historic voyage to Australia and the South Pacific from 1768 to 1771 it was re-fitted into a transportation vessel.

It was used renamed the Lord Sandwich and in 1775 was used to take German mercenaries to Newport and New York before its final refit into a prison ship.

Divers on Thursday carefully took four samples from the potential Endeavour.

Three will be delivered to separate laboratories around the world, with one location possibly Australia, to confirm if it is timber grown in the north of England in the early part of the 18th century.

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That would match the timber used for the Endeavour.

The other sample would be stored and archived.

Other key indicators it is the Endeavour will be if the shipwreck is a 360 tonne vessel and if it was a prison ship.

"What will ultimately determine which of the ships is Endeavour is if we are lucky enough to do an excavation that finds evidence that it was used as a prison hulk," Mr Sumption said.

"That will be the definitive evidence really."