Anemones
Often mistaken for plants, anemones are animals. The stinging cells on their tentacles help them capture prey and defend themselves. Some reproduce sexually, others can clone themselves asexually.

Corals
Corals may not seem as though they fit the Cnidarian mold, but put them under a microscope and all becomes clear. Corals are made up of thousands of tiny polyps living in a colony. Each is complete with tentacles--stinging cells and all.

Siphonophores
A Potuguese man-of-war is not a true jelly, but rather a close relative called a siphonophore. This is another colonial animal with specialized polyps for feeding, stinging, and reproduction, all hanging from a gas-filled float.

Sea pen
It looks like an ostrich plume pen, but it is yet another colonial cnidarian. The center stalk roots itself in the sandy bottom and supports thousands of tiny polyps that filter feed on plankton.

Hydroids
The parade of colonial creatures continues with the hydroid. Hydroids are brushlike colonials that grow on pilings, rocks and shells. They have specialized polyps for feeding, , defense and reproduction.

Comb jellies
These aren't really jellies at all. In fact, they aren't even Cnidarians. They make up their own phylum, Ctenophora. which include 100 species that all have eight rows of iridescent comblike plates used in locomotion.