In all fairness, the studies are rather preliminary and more research is needed before a direct link is established between chemical sunscreen and coral bleaching, but I'm on the side of Better Safe Than Sorry. If switching to an environmentally safe sunscreen means a little less toxic slurry will be swirling through the ocean, then I'm all for it.
If you feel the same way, look for natural sunscreens (no parabens, silicone, or petrochemicals) that use mineral sun filters like titanium dioxide and zinc oxide. I dug around a little and found two that seem to be about as ocean-friendly as you can get: Any sunscreen from Badger and Soleo Organics SPF 30+. I fully plan on taking both of these brands on my upcoming trip to Bora Bora. I don't want to be responsible for trashing paradise!