captain cook HMS Endeavour
Captain Cook's HMS Endeavour Wellcome Trust/CC

The wreckage of Captain James Cook's HMS Endeavour is believed to have been discovered off the American coast of Rhode Island, New England, almost 250 years after it was last seen. Archaeologists at the Rhode Island Marine Archaeology Project (RIMAP) say they are between 80 and 100% sure of the location of the shipwreck, which was sunk in Newport Harbor in 1778.

The Endeavour was the ship used by Cook on his first voyage across the Pacific Ocean to Australia and New Zealand between 1769 and 1771. In the years that followed, the ship was renamed as the Lord Sandwich and was used as a transport ship during the American Revolutionary War.

In 1778, it was one of 13 ships that were deliberately sunk in Newport Harbor in order to create a blockade in the Battle of Rhode Island. However, the exact location of the shipwreck has remained a mystery.

Researchers at RIMAP have now mapped nine archaeological sites of where the ships were sunk in the harbour. One of these sites includes a cluster of five shipwrecks, and archaeologists believe the Endeavour is among them.

The team used historic documents and remote sensing data to find the fifth site. "RIMAP now knows the general area of Newport Harbor where those five ships were scuttled, and in previous work had already mapped four of the sites there," a statement read.

"A recent analysis of remote sensing data suggests that the fifth site may still exist, too. That means the Rhode Island Marine Archaeology Project now has an 80 to 100% chance that the Lord Sandwich is still in Newport Harbor, and because the Lord Sandwich was Capt. Cook's Endeavour, that means RIMAP has found her, too."

The team is set to announce plans to confirm the fifth wreckage site and how it will determine which ship is the Endeavour. "The next phase of the archaeological investigation will require a more intense study of each vessel's structure and its related artefacts," a RIMAP spokesman said.

The announcement comes as Rhode Island prepares to celebrate the 240th anniversary of declaring independence from the UK. "All of the 13 ships lost in Newport during the Revolution are important to American history, but it will be a national celebration in Australia when RIMAP identifies the Lord Sandwich ex-Endeavour. So for RIMAP to be closing in one of the most important shipwrecks in world history, for that ship to be found in Newport, and for it to have an international reputation, should be an intriguing birthday gift for all of Rhode Island," the RIMAP explained on its website.