Oxybenzone, also known as benzonephenone-3, is a common chemical filters found in sunscreens.
It forms colorless crystals that are readily soluble, and provides UV coverage.
There are studies showing that thousands of tons of sunscreen are ending up in our oceans and killing coral reefs. Apparently toxic to coral, as the sunscreens are used by beachgoers the chemical enters the water and kills the closest coral to shore. Hawaii could be the first state to ban the use of sunscreens with these chemicals. The sunscreen lobby is fighting any efforts to ban the use.
There are alternatives and responsible producers are moving to other chemicals in light of the studies.
A TIME story in 2011, lists the products to avoid and those with the highest scores recommended by consumer reports.