However, coral may actually make up less than half of the material in a reef with other organisms binding the various components together as a habitat. Any submerged feature, including those made of rock or manmade materials may be referred to as a reef.
Reefs are primarily a habitat for a wide variety of plants and animals.
They flourish when the surrounding seawater is relatively nutrient poor, largely because they can utilize nutrients very effectively. Their species diversity is rivaled only by tropical rain forests. Reef inhabitants include many types of algae and several invertebrates, such as hard and soft corals, anemones, sponges and many species of arthropods, such as lobster, crabs and shrimp. An amazing variety of fish is also characteristic of reefs. These organisms use this unique habitat for feeding, breading and sleeping.