The picture attached is the drywall next to the tub insert in our master bathroom. I'm not sure how it didn't happen until after my wife and I bought this house and moved in, but the tub/shower insert is a crappy design that has no lip along the edge to keep water INSIDE the insert. So, every time somebody takes a shower, any water that makes its way onto the edge of the tub or on the backsplash (if that's what you call it) inevitably runs off the edge and straight onto the drywall. (BTW- this is the faucet end of the tub shown in the picture). I tried to put a little caulking "lip" to see if it'd do anything but it doesn't really seem to help, and the damage was already done by that point anyway. If I repair this with drywall it will just do this crap again. What is my best solution here? I'd like something permanent that will protect the wall.

Is wet sanding easy to do for a beginner? Any negatives? We need to sand a new ceiling in my daughter's basement, 18' X 18', including 2 soffits. The main reason would be to keep the dust down. Thanks.