The sea squirt, or common sea grape, is an advanced invertebrate that lives in the Chesapeake Bay. It is often greenish-brown and can be found attached to pilings, stones and oyster shells. While it looks like a plant, it is actually a living animal and is considered a tunicate, because of its flexible tough outer covering or tunic.

The creature begins its life as small tadpole-like larvae that can bend from side to side and swim. Once mature, it spends its entire life attached to a solid object. The animal is bumpy with leathery skin and has two openings in which water and food particles enter and leave the body. A sea squirt has both male and female reproductive organs, allowing it to produce and fertilize an egg by itself.

It takes about three days for eggs to develop into larvae that have the ability to adhere to objects. Once adhered, it takes another three days for the sea squirt’s digestive, reproductive and circulatory organs to develop. At maturity, it measures about two inches long and about one and a half inches wide. The animal is very tolerant of pollution and a wide range of salinities, which makes it able to survive along the entire Atlantic coast.