Inca Gold (Dirk Pitt #12) by Clive Cussler

Nearly five centuries ago, a fleet of boats landed mysteriously on an island in an inland sea. There, an ancient Andean people hid a golden hoard greater than that of any pharaoh, then they and their treasure vanished into history -- until now.

1998, the Andes Mountains of Peru. DIRK PITT dives into an ancient sacrificial pool, saving two American archaeologists from certain drowning. But his death-defying rescue is only the beginning, as it draws the intrepid Pitt into a vortex of darkness and danger, corruption and betrayal.