A sea squirt may look more like a vegetable, but it is an animal. Sea squirts are more scientifically known as tunicates, or ascidiaceans, as they belong to the Class Ascidiacea. Even though they don't look like the animals you might normally think of, they are in the Phylum Chordata, which is the same phyla that includes whales, sharks, pinnipeds and fish.
There are over 2,000 species (Source: EOL) of sea squirts, and they are found throughout the world. Some species are solitary, while some form large colonies.
Sea squirts have two siphons - an inhalant siphon, which they use to pull water into their body, and an exhalant siphon, which they use to expel water and wastes. When disturbed, a sea squirt may eject water from its siphon, which is how this creature got its name. Learn more about sea squirts and the Class Ascidiacea here.