starfish,sometimes called sea star, are found in all the world's oceans, even in the icy Arctic Ocean. They are a kind of Ocean invertebrate, which means they lack backbones. All starfish have at least five arms, but some have more. Many kinds of starfish can re-grow arms that are bitten off by predators. Starfish can be dull or colorful and come in many different sizes. Scientists believe there are more than 1500 types of starfish.