Abstract: An underwater communication system comprises a plurality of location and messaging units for sending and receiving ultrasonic energy through water. In accordance with one aspect, each of the location and messaging units comprising an array of four ultrasonic transducers positioned such that they define a generally tetrahedral shape, a transceiver adapted to generate a code element, generate a data element, generate a modulation element, and combine the code element, the data element and the modulation element into an analog wave form. The system is further adapted to transmit the analog wave form through each of the four ultrasonic transducers and receive the analog wave-form generated by at least one of the location and messaging units.