- "In a world of mystery and silence, terror always strikes without warning!"
- — Tagline, from the front cover
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!