Re: What is in waterproof mascara that makes it waterproof?

I'm afraid you are going to disappointed in this one. The ingredients
in modern cosmetics are closely guarded secrets with competing companies
using high powered chemistry to try to determine how to duplicate
each other's products.  The Food, Drug, and Cosmetic Act doesn't require
that they disclose to the customer exactly what is in the products 
although the do perform safety testing on animals, tissue cultures, or 
computer models.

I'd speculate that the 'waterproof' claim (which isn't really true, I'm 
told) implies the presence of a fat. In the old days, this might have come 
from a sperm whale (this is now outlawed), but today the fat could be
either natural or synthetic.

Fats are generally hydrophobic and repell water of course.