Cellular transmission on land is extremely different from communication underwater because an ocean has separate water columns in each of its parts. A transmitter-receiver pair designed to operate at deep sea level will not function in those regions because the characteristics of the water column that exist between the transmitter and receiver will be drastically different from those present in shallow coastal sites. It is more challenging to establish a communication connection since there are so many different types of water bodies. Acoustics is now the most promising technique being utilized to create UWC connection. This tactic is hampered by the multipath phenomenon, which creates a large delay spread. As a consequence, Inter-symbol Interference (ISI) will become worse and reduce system performance. The spread of the delay will be reduced by using OFDM technology. A better method to lessen error bursts in multi-access underwater applications is provided by OFDM combined with IDMA. This study presents an IDMA-OFDM Simulink model. On the BER graph, which showed a BER v/s SNR plot, its performance was evaluated.