The Great Barrier is a giant coral reef off the coast of Australia. It is over 1,400 miles long! There are over 600 different types of coral living in that reef! Coral is often mistaken for a rock because of its hard surface! Many think it is a plant because it is rooted in the ground. Coral is a group of animals!! Different from rocks, coral is alive. Unlike plants, corals do not make their own food. A coral is actually made up of thousands of tiny animals called polyps! These tiny animals use limestone from the seawater to build a hard skeleton around them. That protects the polyps and also makes the coral hard!