No snakes of mine are bathing with any humans! Think of how majorly stressful that would be. BPs like being warm, dry, and safe. A bath would provide none of those things (well maybe warmth.. but not security!) But if it were for the snake's sake (like in a case of retained shed), why on earth would you need to be in there too!
I have bathed with horses though, in a way. I was really hot one 90-degree day, and the horses' water trough was there.. so was I.. it was a great redneck jacuzzi!