Riptide - Douglas Preston

A centuries-old, cursed pirate's treasure valued at over $2 billion lies deep within the treacherous waters off the coast of Maine. Men who have attempted to unearth the fortune have suffered gruesome deaths. Will a high-tech expedition meet the same fate? National ads, including USA Today. For generations, treasure hunters have searched for the key to the Water Pit, the labyrinth of shafts and tunnels that honeycombs Ragged Island. But the Pit is reluctant to give up its treasure, and many will die before its secret is revealed.