Water proof speaker:

SoundLogic AWS-12/2970R Bluetooth Shower Speaker with FM Radio and Carabiner (Red) https://www.amazon.com/dp/B01BFIAL6I/ref=cm_sw_r_cp_api_HYey...

I recently got this and am happy with it so far: https://www.amazon.com/gp/product/B00MYYCGKW

I have something almost identical to this (except the brand was Bush, probably just a white label). It sounds great & works well, but I stopped using it because the volume controls are hard to adjust precisely. You have to press & hold, and the volume ramps up too quickly. If I was buying another I'd look for something where the volume controls are separate from the forward/back buttons.

It was very good quality in every other respect, though.

Edit: For reference, the one I bought: http://www.bushaustralia.com.au/product/water-resistant-blue...

There's some good waterproof BT speakers, as well as some phones are waterproof enough to come into the shower with you (been doing this with my iphone 7, and just bought a speaker)

I have 2 of these, excellent battery life:

AquaAudio Cubo - Portable Waterproof Bluetooth Speaker with Suction Cup for Showers, Car, etc. - Pairs with All Bluetooth Devices + Siri Compatible - 10 hours Playtime/ Built-in Mic (Silver) https://www.amazon.com/dp/B01G7KJV2Y/ref=cm_sw_r_cp_api_.Nuy...

I find my iPhone (6s) speaker, when turned all the way up, is loud enough if I aim the speaker to bounce the sound off of a wall opposite to the shower. In my case it's far enough away that it doesn't get hit by any water.