ROCHESTER -- Two upstate New York underwater explorers say they have discovered a rare dagger-board schooner in the very deep water off the southern shore of Lake Ontario, west of Rochester.

Jim Kennard and Dan Scoville located the ship using deep scan sonar equipment. Kennard says vessels of this type were used for a short time in the early 1800s. The ship is the only dagger-board known to have been found in the Great Lakes.

The shipwreck was found upright and in remarkable condition considering it had plunged more than 500 feet to its resting place on the bottom.

Scoville says the schooner's origin is a mystery so far.