There are more than 10,000 species in the phylum Cnidaria, most of which are marine. The phylum contains hydras, jellyfish, sea anemones and coral animals. Simple, sac-like body. Cylindrical form which adheres to the substratum by the aboral end of the body stalk and extends tentacles around the oral end to contact prey. Moves freely in water by passive drifting and weak bell contractions.
Tentacles dangle from the oral surface which points downward.
Cnidarians are carnivorous.