<P> The water vascular system is a hydraulic system used by echinoderms, such as sea stars and sea urchins, for locomotion, food and waste transportation, and respiration . The system is composed of canals connecting numerous tube feet . Echinoderms move by alternately contracting muscles that force water into the tube feet, causing them to extend and push against the ground, then relaxing to allow the feet to retract . </P> <P> The exact structure of the system varies somewhat between the five classes of echinoderm . The system is part of the coelomic cavities of echinoderms, together with the haemal coelom (or haemal system), perivisceral coelom, gonadal coelom and perihaemal coelom . </P>

Name and describe the opening of the water vascular system