Starfish or
sea stars are star-shaped
echinoderms belonging to the
class Asteroidea. Common usage frequently finds these names being also applied to ophiuroids, which are correctly referred to as
brittle stars or "basket stars". About 1,500 species of starfish occur on the seabed in all the world's oceans, from the tropics to frigid polar waters. They are found from the
intertidal zone down to
abyssal depths, below the surface.