A coral reef is a diverse underwater ecosystem made up of colonies of tiny animals called coral polyps. These polyps secrete calcium carbonate, which forms a hard structure that provides habitat for many marine species. Coral reefs are often found in warm, shallow waters and are known for their vibrant colors and rich biodiversity. Coral reefs support a wide variety of marine life, including fish, mollusks, and sea turtles. They play a crucial role in protecting coastlines from erosion and provide resources for fishing and tourism. However, coral reefs are threatened by climate change, pollution, and overfishing, making their conservation essential.