I once dropped my SE into a fish tank. I got it out in about a second, but considering it's not water resistant at all and it's still working... I'd assume a phone with any sort of waterproofing would be OK as long as the phone isn't directly in the stream. So maybe a bath would be a better idea?
I usually have my phone on the bathroom counter while I'm showering, and I haven't noticed any issues doing that. Again, it's an SE, so I would imagine an X/R/11 would be just fine as well.
Why not? It's advertised as water resistant.