Marine crabs are crustaceans found in oceans around the world. They belong to the order Decapoda, which means they have ten limbs. These creatures have a hard exoskeleton, a broad carapace, and typically walk sideways. Marine crabs play essential roles in their ecosystems, serving as both predators and prey. There are over 6,800 species of marine crabs, including well-known types like the blue crab and king crab. They inhabit various environments, from coral reefs to sandy ocean floors. Crabs are omnivorous, feeding on algae, mollusks, and detritus, which helps recycle nutrients in their habitats.