Underwater Communication using arduino

I am working on a submarine project where I need to communicate with servo motors and send speed and direction and so. I am looking for a solution that helps me communicate with arduino for at least 100 meters. I tried xbee and it works. but connection cuts after 15-20 meters. any ideas or suggestions ?

A 2.4GHz XBee (or similar frequency anything) is not a good choice. You want to use as low a frequency as possible. From the projects I've seen the older, 27MHz RC frequencies are typically used.

If you're aiming for 100 meters of depth then you need to use a tether (wire). You won't find any non-professional (reasonably inexpensive) product capable of that depth.

I think you may need something like this
http://www.dspcomm.com/products_aquacomm.html

Or perhaps fiber optic link from device to device.

Googling underwater wireless communication projects brings up some interesting stuff.

Try this one http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=36&cad=rja&uact=8&ved=0CDwQFjAFOB5qFQoTCJiVq8PxgMcCFQp8kgodYF4Odg&url=http%3A%2F%2Fmy.fit.edu%2F~swood%2FJohn%2520Claus%2520Technical%2520Paper.pdf&ei=QxC5VdjnIYr4yQTgvLmwBw&usg=AFQjCNHT91a6QXHD3MixK8cJjmEp5fodSA

CrossRoads: Try this one http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=36&cad=rja&uact=8&ved=0CDwQFjAFOB5qFQoTCJiVq8PxgMcCFQp8kgodYF4Odg&url=http%3A%2F%2Fmy.fit.edu%2F~swood%2FJohn%2520Claus%2520Technical%2520Paper.pdf&ei=QxC5VdjnIYr4yQTgvLmwBw&usg=AFQjCNHT91a6QXHD3MixK8cJjmEp5fodSA

That is a very cool hack.

The paper describes using an underwater speaker to transmit to the Arduino.