When you can transmit data on a wired or wireless line in air, why can’t you do the same underwater..!! Of course, you can. Here is an interesting project by young engineers at Cornell University presented as their final year project design curriculum. It is specially designed to cater to the future needs of Cornell University Autonomous Underwater vehicle team (CUAUV).
The Acoustic Data Modem is establishes communication at the physical layer of the standards. It consists of a transceiver pair and supports duplex communication. Due the physical properties of acoustic waves, it is possible to propagate these waves underwater at an acceptable rate. The range of operation is human audible range; that is 20Hz – 20KHz. Besides the economical benefits, the device also consumes lesser bandwidth to its other counterparts as it uses the digital on-off keying method for encoding the data. Microcontroller ATmega644 is used to drive the transceiver system.
The modem currently operates in air but this experiment will definitely breed an analogous system that could operate underwater aswell.