Coral reefs are some of the most diverse ecosystems on Earth. Known as the “rainforests of the sea,” they are home to more than a quarter of all marine species. Yet the beauty and vitality of the coral reef environments are threatened—and the reasons are numerous. Rising water temperatures due to climate change, land-based pollution, and indiscriminate fishing practices are the primary threats to coral reef health. Recreational activities like boating, scuba diving, and snorkeling, if done carelessly, can also seriously stress coral reefs. If these stressors continue, they can lead to coral bleaching, and recently the world’s corals have been facing more frequent and severe bleaching events.