Coral reef are the characteristic feature of phylum:

Explanation

Coral reefs are the characteristic feature of the phylum Cnidaria. Cnidaria is a phylum of aquatic invertebrates that includes corals, sea anemones, jellyfish, and hydras. Cnidarians are characterized by their radial symmetry, the presence of nematocysts (stinging cells), and a gastrovascular cavity (a single opening that serves as both a mouth and an anus). Coral reefs are built by colonial cnidarians called scleractinian corals. Scleractinian corals secrete a hard calcium carbonate skeleton that supports the reef structure. Coral reefs are found in warm, shallow waters around the world and are home to a wide variety of marine life.