Deep trouble

"In a world of mystery and silence, terror always strikes without warning!

Long-lost treasure beckons Frank and Joe to a deep-sea adventure in the Bahamas. The Hardys join a crew of divers seeking to unlock the gold-laden vaults of a long-ago shipwreck. But promise soon turns to peril as the treasure hunters become the hunted -- and the Hardy boys become the targets of sabotage!

Frank and Joe discover that beneath the ocean's surface lurk the deepest dangers. They plunge into a world of supercharged speedboat chases and underwater combat and are drawn into a deadly game in which the winners go for the gold and the losers go to the sharks!"

(Hardy Boys Encyclopedia 1991)