Most sunscreens harm corals. Here's what you can do

Every time you go for a swim, some of your sunscreen gets left behind. An estimated 25% of applied sunscreen washes off during recreational water activities, releasing some 5,000 tons annually in reef areas alone, according to a study in Environmental Health Perspectives. That's equivalent to the weight of about 1,000 elephants, and many of those chemicals are toxic to corals. Some researchers argue that may be a low estimate, noting the experiment did not replicate the friction caused by swimming, which could cause more sunscreen to rub off.