Known as the killer whale despite technically being the world's largest dolphin, the orca is the ocean's most intelligent and ruthless predator. Hunting in pods with coordinated strategies that include creating waves to wash seals off ice floes, they've been observed killing great white sharks purely for their livers. The apex predator of apex predators—nothing in the sea hunts an orca.

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.