Re: What is in certain sunblocks that make them waterproof?

There are many chemical which make up sun block or sun screen. Most of 
what makes the sun block waterproof are chemicals in the sunscreen which 
are not water soluble. The resource which I found most useful was 
Healthanswers.com and I searched for sunscreens. There was a lengthy 
article available which described how and why sun screens work. The URL is 
below which links directly to the article, but if that doesn't work, go to 
Healthanswers.com and search for sun screens.
 
http://www.healthanswers.com/centers/body/overview.asp?id=skin+and+hair&filename
=001869.htm


The above link is for the sun screen article which I mentioned. I hope 
this helps you out.....