Final answer:
Sea squirts have a well-developed water vascular system that aids in gas exchange, nutrient circulation, and movement.
Step-by-step explanation:
Echinoderms, including sea squirts, have a unique water vascular system. This system helps them with gas exchange, nutrient circulation, and movement. It consists of a central ring canal and radial canals that extend along each arm. The water vascular system allows sea squirts to slowly move, and their tube feet can be extended and retracted using the hydrostatic pressure in the system. Overall, sea squirts have a well-developed vascular system that plays an important role in their survival and function.