Explorer Capt. James Cook's ship the Endeavour likely found

Researchers say they believe the ship that 18th century explorer Capt. James Cook used to sail around the world is still submerged somewhere in Rhode Island's Newport Harbor, but it'll take a lot of work and money to identify it.

The Rhode Island Marine Archaeology Project, which is leading the search effort, said at a news conference in Providence on Wednesday that it has narrowed its search to a group of five sunken wrecks.

The vessel

Nearly 250 years ago, Capt. James Cook ran aground on Australia's Great Barrier Reef during a voyage to the South Pacific to observe the planet Venus. His ship was the Endeavour, an ugly and awkward little vessel that improbably helped him become the first European to chart Australia's east coast.

Cook used the Endeavour to claim Australia for the British during his historic 1768-71 voyage.

"The Endeavour is considered to be the founding vessel for Australia," said Kathy Abbass, founder and executive director of the Rhode Island Marine Archaeology Project. "She's important in all of the Pacific Rim countries, she's important to England and she's important as well to the whole world because of the scientific information brought back."

Its demise

The Endeavour was part of a fleet of 13 ships the British scuttled during the Revolutionary War in 1778 to blockade Newport Harbor from the French, Abbass said.

It was listed in the records under a different name, the Lord Sandwich.

In 2014, the Australian National Maritime Museum signed an agreement to help the Rhode Island group find the lost vessel. The museum hopes to locate the wreck in time for the 250th anniversary celebrations of Cook's voyage.

What researchers know

The Rhode Island Marine Archaeology Project recently used a grant from the Australian National Maritime Museum to locate documents in London identifying the groups of ships in that fleet and where each was scuttled.

The nonprofit thinks the Endeavour is part of a group of five sunken wrecks.

It already has mapped nine of the 13 sites in the harbor, including four of the five sites in that group, Abbass said.

"We know there were five. We know we mapped four. We think we can find the fifth one," Abbass said. "That's for this year, to find the fifth one."

What they don't know

Remote sensing data appears to show the fifth site, but it could be badly disturbed, Abbass said. She said she won't know for sure until divers investigate.

Even if all five sites are located, Abbass said she may not find enough conclusive evidence to say that one of them is the Endeavour.

What's next

Abbass said she'll need to raise millions for archaeological field work and to build a facility for artifacts.

She estimates the field work would cost about $1 million and the facility would cost $7.5 million.

If the Endeavour is found, it will belong to Rhode Island, she added.

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