Most sunscreens are petroleum-based and unfortunately non-biodegradable. Sunscreen is super toxic to coral, and have caused large scale coral bleaching world wide. Instead of a chemical-based environmentally dangerous sunblock, try opting for an organic alternative. This also applies to moisturizers with SPF, so keep an eye out when hunting for your next sun-blocking face lotion. The coral reefs (and your skin!) will thank you!