The term “crab” refers to the walking decapods, the crustaceans that are able to swim in water and walk on land. Crabs are characterised by a relatively small abdomen, tucked under a rigid and rounded carapace (shell), and five pairs of legs. The crab’s main pair of legs are equipped with strong claws that they use to grip and crush their prey. It also walks sideways, allowing it to be faster. Some crabs dig burrows in the sand and crawl out so swiftly that they are named ghost crabs.