A sea lily is a type of crinoid, which is a marine animal belonging to the phylum Echinodermata. Crinoids have a stem and five or more arms that are used for locomotion and feeding. Sea lilies are sessile animals, meaning they are attached to the seafloor and do not move around. They are filter feeders, meaning they feed on small particles in the water. Sea lilies are found in all oceans and can range in size from a few millimeters to over a meter in length.