Water Vascular System is a unique system of echinoderms which helps mainly in locomotion. It is in fact a modified part of coelom consisting of a system of canals containing sea water and amoeboid corpuscles.
Phylum Echinodermata (Gr., echinos = hedgehog ; derma = skin) is a group of marine invertebrates characterized by radial symmetry, a calcareous endoskeleton, and a water vascular system used for locomotion, feeding, and respiration. Members of this phylum include starfish, sea urchins, sand dollars, and sea cucumbers. They exhibit pentamerous symmetry in adults, have a unique regenerative ability, and possess tube feet for movement and adhesion. Echinoderms are exclusively marine and play essential roles in ocean ecosystems as predators, grazers, and sediment stabilizers.