Offshore are numerous coral reefs and tiny islets. Over 4,000 species of fish inhabit coral reefs. Reef types include fringing reefs, barrier reefs, and atolls. Algae and corals in coral reefs produce organic material. They inhabit the deep slopes of coral reefs. There are 187 species of coral forming the coral reefs. They live in sheltered areas such as seagrass beds, estuaries, coral reefs, and mangroves. Coastal communities near coral reefs rely heavily on them. The island is surrounded by coral reefs. They tend to school around coasts and islands with coral reefs. Explosions are particularly harmful to coral reefs. Barracudas reside near the top of the water and near coral reefs and sea grasses. The island covers and has several coral reefs. These islands have a collection of coral reefs. Most fishes are typical of coral reefs, such as butterflyfish.