There was an interesting article on sunscreens in the NY Times a few weeks ago (registration may be required). Most interesting to me was the site they referenced with ratings for the different brands. I had been buying Coppertone Sport SPF 50 for golfing and it seemed to be effective. However, it's definitely not top tier. I'm going to try out the Blue Lizard Sensitive SPF 30 which is on the first page of the top rated list below.

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[ NOTE: the links for the ratings site ask for an email address but you can bypass that by clicking on the link below the input box ]