Abstract: An underwater apparatus for transmitting and receiving high rate data and voice communication including a transmitter, a receiver, and a Doppler frequency shift compensator. The transmitter includes a data source comprising digital data to be transmitted by the apparatus through the water, a serial-to-parallel data processor for splitting the serial digital data into n parallel data channels, a n-channel modulator for receiving the n parallel data channels and for modulating those channels with n pairs of ultrasonic carriers to produce a modulated signal. The transmitter also includes a hydrophone for receiving and transmitting the modulated signal. The receiver includes a hydrophone for receiving a modulated signal.

Abstract: A personal underwater communication device which comprises: A display; A memory unit for storing a plurality of preset messages, each message being assigned a common message identification code; Means for assigning a unique identification code to each personal device; Means for selecting one of said preset messages, to be transmitted to a receiving device; Means for selecting one or more receiving devices to which a message is to be transmitted; Means for producing a string encoding said message identification code and the identification code of the transmitting device; Means for modulating said string with at least one ultrasound acoustic modulating frequency, thereby to produce a modulated signal; Means for transmitting said modulated signal in water; Means in each device for receiving transmitted ultrasound acoustic modulated signals; Means for demodulating modulated signals which are received by said device, thereby to produce a demodulated string; Means for decoding a message from said demodulated string