Starfish, also known as sea stars, are marine invertebrates that live in oceans around the world. They have between 5-44 arms that radiate from their central disc in a symmetrical pattern and come in a variety of colors. Starfish move slowly by crawling and climbing rather than swimming. They feed on mollusks like oysters and mussels by wrapping their arms around the shell and pulling until it opens. Despite their name, starfish are not fish - they have no brain, blood or internal skeleton.