In Jamaica, salvage divers Brad and Tony (Robert Ryan and Anthony Quinn) are hired by Dwight Trevor (Karel Stepanek) to find "The Lady Luck", a ship that was supposedly sunk with all hands and $1,000,000 in gold bullion. There is no trace of the sunken ship, but there is a sunken city, the city of Port Royal that was destroyed in an earthquake in 1692. The $1,000,000 in gold bullion was in fact lost in a modern-day quake and is part of an insurance fraud by Trevor. He does not want the divers to find the gold and will stop at nothing to ensure the success of his plan.