If water is transparent then why cant you use cell phones underwater?

Answer 1

Only b/c water is transparent to the Eye doesn't mean it's transparent to the antenna of the cell phone. Water is an effective barrier for the frequency range for cell phones, and would quickly kill all signal.

=====

Of course the biggest reason is that few cell phones are waterproof. If they get wet, they short out.

In fact, you CAN use a waterproof cell phone underwater - within limits. Until you get a waterproof cell phone far enough underwater, they DO work underwater. Once you get them deep enough the signal strength will diminish enough to make them not work - just like going far enough into or into the basement a building without a signal repeater will diminish the signal so much that you can't get a connection. Also it won't work very well to try to talk on the phone underwater because the microphone and speaker are made to work in air and water, being much, much, much, much, much denser won't conduct sound the same way. You could probably play some games or text people if the water was shallow enough and the cell tower was close enough.