One of the greatest maritime mysteries of all time could be solved with the apparent discovery of HMS Endeavour — the ship James Cook captained on the first voyage to Australia.

Marine archaeologists are expected to announce a breakthrough in the 25-year search for the historic 250-year-old vessel on Friday.

It's believe the ship's final resting place is in Newport Harbour, off Rhode Island on the northeast coast of the US. The search has been narrowed down to an area just off the Goat Island shore near Gurneys Resort.

Archaeologists from the Australian National Maritime Museum (ANMM) and the Rhode Island Marine Archaeology Project (RIMAP) will release a 3D photogrammetric image of the site at the official announcement in the US later this week.

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But the origins of the ship can't be confirmed until its remnants are excavated - which researchers expect will happen next year.

RIMAP director Kathy Abbass told Fairfax that researchers were "closing in" on the shipwreck after she located historical documents in London that guided her team to Newport Harbour.

"Now that RIMAP and the ANMM have identified a possible site in Newport Harbour that might be the Lord Sandwich ex Endeavour, the detailed work must begin to prove it," Dr Abbass said in a statement posted on the group's website on Tuesday.

"Therefore, fundraising is ongoing for the artefact management facility needed to process, store, and display the artefacts that will emerge from the planned 2019 excavation."

The Endeavour was purchased by the British Navy in 1768 and navigated by Cook to claim Australia — then known as Terra Australis — for the British during his historic voyage.

It became the first ship to reach the east coast of Australia when Cook arrived at the site now known as Botany Bay in 1770.

The ship was later renamed the Earl of Sandwich 2 and last seen in 1778 while being used for transportation purposes during the American War of Independence. Researchers believe the Endeavour was part of a fleet of 13 ships scuttled by the British during the Revolutionary War to blockade Newport Harbour from the French.

RIMAP started studying sunken British transports in Newport Harbour in 1993 with a remote sensing survey.

There were 13 potential vessels that could have been the Endeavour but the search has recently narrowed to possibly "one or two archaeological sites", RIMAP said in a press release.

Portrait of Captain James Cook, c. 1780, oil on canvas in Museum of New Zealand. Photo / Getty Images
Portrait of Captain James Cook, c. 1780, oil on canvas in Museum of New Zealand. Photo / Getty Images

Past theories about the ship's final resting place include that it was at the bottom of the Thames, somewhere between Woolwich and Greenwich in London, after spending its final days acting as a receiving home for female convicts and then as a home to an "old pensioner" and his family.

A replica of the Endeavour was launched in 1993 and is berthed at the Sydney's Australian National Maritime Museum, an image of the vessel is on New Zealand's 50 cent coin, and NASA's space shuttle Endeavour was named after Captain Cook's ship.

Australian National Maritime Museum chair Peter Dexter will travel to the US along with Australia's Consul-General in New York Alastair Walton for the announcement regarding the breakthrough on Friday.

Despite the historical significance to Australia, it is likely the Endeavour, if found, will remain in Rhode Island.

In 1999 former Rhode Island Attorney-General Sheldon Whitehouse legally ensured Rhode Island's ownership of the historic Newport fleet, including the Lord Sandwich.

The Rhode Island Historical Preservation and Heritage Commission is also the custodian of the Newport Harbour shipwrecks.

The Rhode Island Coastal Resources Management Council has also established a "No Anchor - No Dive" zone around the archaeological sites to protect them. This year marks the 250th anniversary of Cook's departure from England on the Endeavour.

The public is being asked to donate to RIMAP to help finance an artefact management facility needed to process, store, and display the artefacts that will emerge from the planned 2019 excavation. Donations can be made through PayPal on the RIMAP website.