A new thriller from the USA TODAY-bestselling master of undersea adventure

Tiller Galloway, black-sheep hero of HATTERAS BLUE, BAHAMAS BLUE, LOUISIANA BLUE, and DOWN TO A SUNLESS SEA, is back! When the IRS begins asking how a blue-collar oilfield diver and ex-con drug smuggler ended up so rich, Galloway flees with his son Max to Cancun, Mexico.

There, July Toll, whom Tiller knew from cave diving in Florida, has been hired to help hunt for a mysterious "Site X," associated with the collapse of the Mayans circa AD 900. Archaeologists had been searching for it for years, following a trail of looted artifacts marketed through art dealers. Now, Mayanist Dr. Benton Hardinge and his associate Dr. Kinsey Yang-Jensen think they've located the ancient city through satellite imaging. But it's not on land, but deep beneath a cenote-fed lake in the thick jungle of remote South Yucatan.

In the face of a peasant revolt, corrupt federales, murderous looters, and the mortal terror of deep rebreather diving, Galloway, Max, and July struggle to penetrate the sunken temple complex. But they've stumbled on more than the solution to an ancient mystery. Unless they can stop it, the same evil will be unleashed on the world that destroyed the Mayan Empire a thousand years ago....