It is what was recommended, I’m assuming because then you know you’ve changed it too? Plus it leaves a little sticky stuff residue from the edges of the patch, takes a few days for me to easily rub it off and a new one won’t stick well on top of the mark. Does that make sense? Yes you can get it wet, no problem. It says you can take a bath and swim too, but on the day I applied one I think it wasn’t the best idea. I decided if I want a soak in a bath I’ll do that on a day I’m about to change it, before I put a new one on, not after. I’m going swimming soon so I’ll find out if it sticks ok then. It’s better to take a shower before you apply one, rather than after as it takes a while to fully be stuck on well and can bubble a bit if you shower afterwards. But usually showers don’t matter to it at all.