Unchanged for 200 million years because evolution couldn't improve the design, the saltwater crocodile is a 2,200-pound ambush predator with the strongest bite ever measured in the animal kingdom. Its death roll can dismember prey in seconds, and it can lurk motionless for hours before exploding from the water at terrifying speed. Dinosaurs went extinct; this thing didn't.

Patrolling the world's oceans for over 400 million years of evolutionary refinement, the great white shark is nature's most efficient killing machine. Armed with 300 serrated teeth and electroreceptors that detect a heartbeat from yards away, nothing in the sea is safe. A single bite delivers up to 18,000 newtons of force—enough to chomp through bone like breadsticks.