Water vascular system is found in  

The correct answer is Echinodermata.

Explanation-

Echinoderms, a group that includes sea stars (starfish), sea cucumbers, sea urchins, sand dollars, and brittle stars, possess a unique structural feature known as the water vascular system.

The water vascular system is a network of water-filled canals that function in locomotion, feeding, gas exchange, and sensory perception. Here's how it generally works:

• Water Inflow: Seawater enters the system through a sieve-like structure on the echinoderm's body surface called the madreporite.
• Stone Canal: From the madreporite, water then flows into a short canal, often lined with calcareous material, known as the stone canal.
• Ring Canal: The stone canal leads to a circular canal, the ring canal, that surrounds the esophagus.
• Radial Canal(s): Connected to the ring canal are five (or multiples of five) radial canals. These extend into each of the echinoderm's arms (if arms are present).
• Tube Feet: Off of the radial canals are many lateral canals, each terminating in a muscular, often sucker-tipped, extension known as a tube foot or podium. The sequential contraction and expansion of the tube feet, controlled by the water pressure within the canals, assist with locomotion, enable feeding, and facilitate gas exchange.

The water vascular system in echinoderms allows these marine animals to move effectively despite having no centralized brain nor discernable front or back to their bodies.

Conclusion- Water vascular system is observed in Echinoderms.