Sea stars can have five or more thick arms. With different species, the arms can be flexible or rigid. At the end of each arm is a tiny eye that can detect light and dark. Some sea stars are strong enough to open bivalve shells such as small clams.
The tube feet are under the arms and enable sea stars to move slowly and cling to rocks. Many sea stars can push their stomachs out of their mouth and cover the food they want to eat.
They can start digesting their food before pulling their stomach back into their mouth.
Most types of sea stars are carnivorous hunters, but they may also eat seaweed and decaying material. Their mouth is under their body and their anus is at the top of their body.