Seems pointless and inconvenient for me as they usually seem to be poor quality, and can you really listen to music in the shower, and are you showering long enough to benefit from it?
Or do you own one and use for a different purpose, like swimming or Kayaking?
I have a Sonos portable speaker that I keep in the kitchen but take into the bathroom while I shower. It just sits on the shelf outside the shower. I like music while I shower, and doing it this way keeps good quality without risking the speaker.