Underwater 2-way Radio

I have no plans on making this but i was reading another post then i started day dreaming and thought of it.

How would you build a transceiver that could transmit audio/data/or what ever, and transmit it using soundwaves.

so say i got a dolphin next to me and he wispers a sound into the 2-way and i take that and amplify it the transmit it through the water using soundwaves and then my dolphins friend can hear the message on the radio he has stuffed in his pocket

Im a weirdo but if you were to do it how would you?

where would you get a waterproff mic from?

You have obviously dome some reading because you did not say "radio" in your post.Allthough radio waves will work for low data rates but not real time speech.
Freaquency Modulation and Demodulation are the key circuits, hunt around the web for these devices have been around since the early sixties.
Oil drilling companies have been using a similiar idea, sending data from sensors in the drill bit head up to the surface by sound pulses conducted up the pipe through the "mud"

Here are a few links worth following..................
http://english.pravda.ru/main/18/89/357/9991_communication.html
http://www.divelink.net/
**broken link removed**

Radio Related....
http://www.qsl.net/vk5br/UwaterComms.htm
http://www.rexresearch.com/rogers/1rogers.htm

The military magazine "Jane's" might also be worth searching.