Juan Cabrillo and the crew of the covert combat ship Oregon have barely escaped a mission on the Congo River when they intercept a mayday from a defenseless boat under fire off the African coast. Cabrillo takes action, saving the beautiful Sloane Macintyre-who's looking for a long-submerged ship that may hold a fortune in diamonds. But what surprises Cabrillo is her story about a crazy fisherman who claims to have been attacked on the open sea by giant metal snakes in the same area.