MIMO-OFDM IDMA is used to reduce fading in underwater wireless communications. MIMO allows data to be delivered simultaneously from several antennas and received by one or more antennas. This strategy increased data rate, preserved bandwidth, and reduced fading. IDMA outperforms all other underwater multiple access techniques. Both MIMO-OFDM and MIMO-IDMA demonstrated low BER with variable user numbers. We combine MIMO-OFDM and IDMA to reduce burst errors and to fade in underwater channels. Underwater wireless communication fades in several ways. Hydrophones and MIMO-OFDM with IDMA improve underwater communication. Underwater communication uses acoustic waves, which have slower data rates than electromagnetic waves. This work reduces low-data-rate fading. This study used IDMA with random interleaving. Future IDMA upgrades may include a tree-based interleaved. Tree-based interleaved is used for pattern generation and user separation.