to follow-up with gross water things, think about the amount of crap and piss in the ocean. now think about the amount of crap and piss in a swimming pool. still gross.
also, i'm grossed out by the idea of a public pool because tons of kids are pissing in it, but i have no problem being in a private pool with a bunch of kids that i know, even though they're definitely pissing in it also.