Trouble in Paradise (Hardy Boys: Undercover Brothers (Prebound Numbered))

The teenage son of a prominent middle-eastern diplomat has gone missing on the Caribbean island of St. John, and the boys take off to find him. It turns out he's been kidnapped by a group planning to rob a sunken Spanish galleon of all its treasures. Frank and Joe search high and low, fighting thugs and sharks, for clues to find the missing boy. But when they do find him, they're in for a big surprise...