This handout image, from video released Friday by Jim Kennard and Dan Scoville, shows the crows nest and foremast of the sunken British warship HMS Ontario.

Syracuse, N.Y. ? A 22-gun British warship that sank during the American Revolution and has long been regarded as one of the “Holy Grail” shipwrecks in the Great Lakes has been discovered at the bottom of Lake Ontario, astonishingly well-preserved in the cold, deep water, explorers announced Friday.

Shipwreck enthusiasts Jim Kennard and Dan Scoville used side-scanning sonar and an unmanned submersible to locate the HMS Ontario, which was lost with barely a trace and as many as 130 people aboard during a gale in 1780.

The 80-foot sloop of war is the oldest shipwreck and the only fully intact British warship ever found in the Great Lakes, Scoville and Kennard said.

“To have a Revolutionary War vessel that’s practically intact is unbelievable. It’s an archaeological miracle,” said Canadian author Arthur Britton Smith, who chronicled the history of the HMS Ontario in a 1997 book, “The Legend of the Lake.”

The finders of the wreck said they regard it as a war grave and have no plans to raise it or remove any of its artifacts. They said the ship is still considered the property of the British Admiralty.

Although the vessel sits in an area where the water is up to 500 feet deep and cannot be reached by anyone but the most experienced divers, Kennard and Scoville declined to give its exact location, saying only that it was found off the southern shore.

The sloop was discovered resting partially on its side, with two masts extending more than 70 feet above the lake bottom.

“Usually when ships go down in big storms, they get beat up quite a bit. They don’t sink nice and square. This went down in a huge storm, and it still managed to stay intact,” Scoville said. “There are even two windows that aren’t broken. Just going down, the pressure difference, can break the windows. It’s a beautiful ship.”

Smith, who was shown underwater video of the find, said: “If it wasn’t for the zebra mussels, she looks like she only sunk last week.”

The dark, cold freshwater acts as a perfect preservative, Smith said. At that depth, there is no light and no oxygen to hasten decomposition, and little marine life to feed on the wood.

The Ontario went down on Oct. 31, 1780, with a garrison of 60 British soldiers, a crew of about 40, mostly Canadians, and possibly about 30 American war prisoners.

The warship had been launched only five months earlier and was used to ferry troops and supplies along upstate New York’s frontier. Although it was the biggest British ship on the Great Lakes at the time, it never saw battle, Smith said.

After the ship disappeared, the British conducted a sweeping search but tried to keep the sinking secret from Gen. George Washington’s troops because of the blow to the British defenses.

Hatchway gratings, the binnacle, compasses and several hats and blankets drifted ashore the next day. A few days later the ship’s sails were found adrift in the lake. In 1781, six bodies from the Ontario were found near Wilson, N.Y. For the next two centuries, there were no other traces of the ship.

Explorers have been searching for the Ontario for decades, and there have been numerous false finds over the years, said Eric Bloomquist, interpretative programs manager at Old Fort Niagara.

Kennard, an electrical engineer who has been diving for nearly 40 years and has found more than 200 wrecks in the Great Lakes, Lake Champlain, the Finger Lakes and in the Mississippi and Ohio Rivers, began searching for the Ontario 35 years ago but quit after several frustrating and fruitless years.

Six years ago, he teamed up with Scoville, a diver who developed the remote-controlled submersible with students from the Rochester Institute of Technology. Since then, the pair have found seven ships in the lake.

Over the years, Kennard obtained documents from British and Canadian archives on the Ontario, including the ship’s design plans. Even then, it took the pair three years of searching more than 200 square miles before they found the vessel earlier this month.

After locating the wreck with the sonar, the explorers used the submersible to confirm their find, documenting their discovery with more than 80 minutes of underwater video.