Coral reefs are large ecosystems built from calcium carbonate secreted by corals. They provide habitat for 25% of marine species despite occupying less than 0.1% of the ocean. Coral reefs flourish in shallow, tropical waters where there is enough light for algae and plankton to photosynthesize. While most prominent in the Caribbean, Indian Ocean, and South Pacific, coral reefs also exist in non-tropical areas like the Red Sea and Great Barrier Reef due to warming currents. The UK has recently discovered cold water coral reefs using underwater cameras that are home to exotic marine life but may be damaged by fishing boats before being explored.