Snorkeling allows one to view coral reefs and sea life through the use of a snorkel, mask, and fins. Coral reefs are fragile ecosystems made up of live and dead organisms that provide shelter for many species. When snorkeling among reefs, one should avoid touching coral or disturbing sea creatures, as both the reefs and wildlife are easily damaged. Common dangers include stings and bites from creatures that feel threatened. Increased pollution, sedimentation, overfishing and climate change all endanger coral reefs. National parks and sanctuaries help protect these ecosystems.