I work in water/wastewater. When I consider the arguments here about environmental responsibility when it comes to sewage, I usually just chuckle. But in the interest of clarity, a lake or ocean is a very large ecosystem that will have no trouble absorbing the effluent from the typical density of recreational boaters. Some may have higher densities and larger issues, but I'm talking averages. If you peed in your neighbours pool, he might get uptight if he found out, but realistically it would only cause his chemical/filtration costs to go up. Remember, urine is water with a nutrient content which can either be chemically inactivated or filtered.
As to the 'other' waste product being discussed. Don't eat it, it's not good for you. If you mix it by hand, make sure you wash them very well before eating your sandwich. If the thought of it being dumped under a random tree or a dumpster upsets you, then you might want to watch pet owners very carefully when they're out walking fido.
I love interweb debates. :/