Electronics and water generally shouldn’t be mixed.
If you want tunes in your bathroom, install a set of shower or waterproof speakers in the bathroom, find a place to put your laptop outside of the bathroom that is in reach of the speakers, and plug it in when you want bathroom tunes. Or, make it easier and use a pair of streaming speakers – however you may eventually face the same situation with non-waterproof speakers as you are trying to avoid with the laptop (corrosion or intrusion of water or humidity causing problems) unless you find a product similar to this one (which is built for iPods, not Macbooks sadly).