Generally, large number of energy constrained nodes are deployed on different depths to sense the required parameter(s) in underwater environment. These nodes are not aware of their exact position; however, their depth can be found using depth (pressure) sensors. In underwater, nodes communicate with each other through acoustic links. As described earlier, there are some immanent characteristics of acoustic communication like, limited bandwidth (<100 KHz), larger delays, and time varying multi path fading  which may cause larger doppler shift. All the deployed nodes also have energy constraint so their efficient energy consumption is of prime importance. It is almost impossible to replace or recharge the batteries of deployed nodes.