Gay men cannot have anal sex in water, whether tub, pool or jacuzzi, because there is not enough natural lubricant to allow for insertion/strokes. Artificial lube or spit lube "washes off" and is ineffective.
You can do oral, but I don't think that'd be too fun since after 30 seconds you need to resurface for air--thereby interrupting the b/j.
Gays can have anal sex in a shower, but the same issue of abrasiveness comes into play. Me and my b/f did it once, and we won't be doing it again. Kind of like we did it on a table once, but won't be doing that again. It was a novelty thing, didn't feel that good and was too much work.
Regarding water "plunged" into your ass or "turds" coming out, what? The amount of water that would get inside would be minimal. Just like it's not good to drink chlorinated pool or treated jacuzzi water, it's not fatal in normal amounts. And the turds coming out, has that ever happened to you during sex? If so, you're not cleaning out correctly.