This section of the bathroom wall will often get the most damage from moisture. If you're using a shower curtain and it's not protecting the bathroom walls, you could find yourself with this kind of damage.

Even if you have a shower door enclosure unit, if it's not sealed properly, you could end up with a situation like this from the water working it's way around the enclosure.

Home Repair Tip - Try to make it a habit, whenever you're in the bathroom or someone else's bathroom, look at this area of the bathroom for damage. If you see any paint bubbling, mold growing, or drywall expanding. There's a good chance that moisture has been accumulating for quite some time now.

As you can see in the picture above, if moisture gets behind the tile, grout or caulking it can very easily work its way around the bathtub and down the front side. With no place for the moisture to go, eventually it will start to damage, the framing, drywall and if you're upstairs, the water will eventually work its way into the floor and ceiling. Bathtub Floor Damage