What is the truth about sunscreen?

I have used Vertra sunscreen on my face for a while now and because I surf almost everyday, I lean towards a higher spf. When I'm not using a wetsuit top or rash guard, I use a high spf, waterproof, and child-formulated sunscreen. I've heard a lot of contradicting things about sunscreen, higher spf ratings, adult vs. child formulas, waterproof vs. not waterproof, and the list goes on and on. What I do know is that the human skin is the largest organ one has and it is imperative that we take care of it. Here is an interesting blog about sunscreen that a classmate wrote.

Dean's SPF blog.