Crustaceans Crustaceans belong to a group of animals called Arthropods, which means hard exoskeleton and jointed limbs. This is one of the most numerous and diverse group of organisms on the planet, and most species of crustacean live in the majority of marine habitats, from hiding under boulders in rockpools to burrowing deep in the sand. Velvet Swimming Crab © Lawson Wood Ocean Eye Films All crustaceans have a hard outer shell, called an exoskeleton, which is made from calcium and protects their soft internal organs. In order for the animal to grow, they must shed this exoskeleton at regular intervals, so look out for them washed up on the beach – what you think is a dead crab may be just its shed skin! Crabs, Hermit Crabs & Lobsters Shrimp & Prawns Barnacles