Most ocean crabs are considered carnivores and eat just about any meat they can find. There are a few species that are omnivores, however, and eat plants as well as meat.
Popular ocean crabs, such as Dungeness and King crab, eat a variety of fish as well as other bottom-dwelling animals such as urchins, starfish, sand dollars and snails. They are also known to eat the eggs of those animals and even hunt members of their own species. Blue crabs tend to be scavengers and feed on many types of dead organisms, but have been known to eat other crustaceans. They also eat live plants on occasion.