I couldn't have put it better myself. I've never been around a public pool of any kind -- at a resort, at a waterpark, at a gym, anyplace -- where the actual bathrooms seemed proportionately busy to the number of people there. But did we need that to know that nearly everyone's peeing in the pool? Besides a few very politely minded people (of which I used to count myself as one, in fact), the fact of the matter is, swimmers pee. If you have a public pool, it will get peed in. It's just a fact of life.
It's also one that I'm happy to contribute to myself. Just like you, and just like @Magg