Red Crabs are creatures in Hungry Shark World that are hostile, they attack by pinching through your body.
They can be consumed by Whitetip Reef Shark, Porbeagle Shark, and Blue Shark, and other bigger sharks. But cannot be consumed by Blacktip Reef Shark due to its small size. when encountered one, you will be pinched by the Red Crab.
Red Crabs usually appears in groups two or three. They can attack from short range. Which makes them lethal, but also allows for a quick health top-up.