Corals are animals! They are invertebrates in the phylum Cnidaria, just like jellyfish and anemones.
Corals may attach to the ground like plants and be hard like rocks, but they are living organisms. Corals are made up of hundreds or thousands of animals called polyps. Each polyp uses stinging cells on its tentacles, which surround the mouth and stomach, to capture food, primarily zooplankton. The polyp builds a skeleton out of calcium carbonate, also known as limestone, from the seawater to protect itself.
