Why are There No Underwater Bluetooth Headphones?

There is no problem creating water-resistant and waterproof headphones, but as of right now we have no wireless technology that would transmit the signal underwater with high enough proficiency.

The water is simply too "dense" and just soaks up all the signal making Bluetooth useless underwater.

This wireless technology doesn't work properly underwater and so far no manufacturer has been able to produce a decent pair of wireless underwater headphones.

For real underwater purposes, you'll have to use wired headphones or headsets together with the underwater music player.