Researchers say they're closing in on Captain Cook's ship

Researchers believe the ship that legendary explorer Captain James Cook used to sail around the world is still submerged somewhere in Rhode Island's Newport Harbor.

The Endeavour was part of a fleet of 13 ships the British scuttled during the Revolutionary War in 1778 to blockade the port.

The Rhode Island Marine Archaeology Project, which is leading the search effort, 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 sites in the harbor, including four of the five sites in that group.

It's announcing plans on Wednesday to investigate the fifth shipwreck this year.