Sea Squirt, a marine animal usually found in coastal areas. Most sea squirts live permanently attached to such objects as rocks, shells, and wharves. They are often brilliant in color and usually globular or cylindrical in shape. The soft body is surrounded by a transparent, flexible outer covering called a tunic. Sea squirts range from 1100 inch to seven inches (0.025 to 18 cm) in diameter.

The adult sea squirt has two structures, called siphons, at the top of its body. One siphon draws in water and the other expels it. The sea squirt feeds on plankton, which it filters out of the water with its pharynx. When disturbed, the sea squirt contracts its siphons, expelling two streams of water—a habit from which it gets its name.

Many sea squirts reproduce asexually by means of budding as well as sexually by means of eggs and sperm. In budding, a new sea squirt develops as an outgrowth of the parent's body. In sexual reproduction, fertilized eggs develop into tiny tadpole-shaped, free-swimming larvae. The larvae have a notochord, a backbone-like structure that eventually disappears when they mature. The larvae swim about for a few weeks before they develop into their adult form.

Sea squirts make up the class Ascidiacea.