There is a general consensus amongst scientists that most chemical sunscreens we use harm coral reefs and other marine life. Many chemicals are toxic for coral, especially Oxybenzone (ps many alternative names exist for it). As a good alternative biodegradable, mineral sunscreens including zinc oxide or titanium dioxide that are “non-nano” in size are considered safe. Important to check the ‘’non-nano’’ of these products which explains the particle size. Smaller particles (‘nano’) can be ingested by the coral polyps and are still harmful. For more info see sunscreen .