Unlike what we're used to in Michigan, if you gotta pee, you don't find a bush or a tree. In the desert, it would quickly evaporate, leaving odor and salts. With little rain, it would not quickly dissipate. Therefore, the rule in the Grand Canyon is you pee in the river. Women upstream, and men downstream. Also voiced as "skirts up, pants down".
This was interesting. We'd earlier noted that all the food for the trip came in. We'd also noted that all of the garbage came out. Garbage included poop. We had 2 toilets that came with us and were the first thing set up at camp and the last thing taken down at camp. We were asked to NOT pee in the toilets. (an exception was allowed for women in the night as we didn't want to have anyone lose their footing and go floating down the Colorado River in the middle of the night).
Two toilets were set up. The first was inside a cabana, and the cabana door would be clipped open/shut as needed.
The second was setup in a secluded area of camp beyond the first. Access to the second was controlled by the yellow "need help ticket". The ticket stayed in camp by the hand washing station until someone needed it and off they went, ticket in hand, knowing that if they had the ticket, no fellow camper would come visit them. The second picture here is the view from the open air toilet. Pretty nice, don't you think?
We've heard stories of folks on the open air toilet waving to boats passing by, but for the entire time we were in camp, I don't believe we ever saw a passing boat. We would encounter others during the daytime traveling, but never in the early a.m. or late p.m. when in camp.