Abstract— This paper presents performance evaluation of differential quadrature phase shift keying (DQPSK) transmission over underwater acoustic channel (UWA). In this paper, a channel model that simulates the multipath fading characteristics of the shallow underwater channel is carried out in order to make possible of performance evaluation of DQPSK transmission. Next, a single carrier DQPSK communication with convolutional encoder is simulated and carried out. The impact of channel capacity is explored as well. The system performance will be measured by the bit error ratio (BER). Investigations of multipaths and transmission distance will be obtained and discussed in details.