The foot attaches to hard surfaces and can also burrow in the sand in certain species. Some anemones glide along their pedal discs like a snail or move like an inchworm. Others let go of their rocks and shells and allow themselve s to be carried in the waves. A northern Pacific species does cartwheels to avoid being eaten, although this movement is very slow. Corals have polyps also, as do most cnidarians at some point in their lives.
Coral polyps grow connected to each other in large groups called colonies.
They also produce a hard, limy skeleton that is the base of coral reefs. Anemones do not grow in col onies or produce skeletons. Instead, anemones are called solitary polyps because they grow as individual animals. One feature that some anemones do share with their relatives is zooxanthellae. Zooxanthellae are single-celled algae that live inside of anem one and coral polyps.