Cnidarians are a large group of soft-bodied marine animals. Sessile forms such as sea anemones that attach themselves to the ocean floor are more often used as food than free-swimming, stinging cnidarians, like jellyfish.
Cnidarians include sea anemones, corals, and jellyfish. All cnidarians make use of stinging cells (cnidoblasts) to discharge a toxic structure when a prey or a predator comes in contact with those cells.