The acoustic channel differs from radio channels in many aspects. Two fundamental mechanisms of multipath formations are reflection of the boundaries and ray bending. So the acoustic channels may have extremely long multipath spreads. In addition, the acoustic signals are subjected to temporal and spatial varying multipath channel, which may result in severe Inter Symbol Interference (ISI) for Underwater Acoustic Communication (UAC). These characteristics restrict the range and bandwidth for reliable communications and lead a low data transfer rate. In order to mitigate the ISI, Time Reversal Technique is introduced. The Bit Error Rate (BER) is calculated for UAC and AWGN for different modulation technique.