Abstract: An underwater communication system by coded pulses, includes a transmitter placed at a surface of a body of water, for transmitting coded pulses, the transmitter having a transmitter circuit for generating the coded pulses, the transmitter circuit including a first shift register pre-programmed with a binary code corresponding to the coded pulses, and an underwater piezoelectric transducer for submersion in the water and electrically connected with the transmitter circuit for transmitting the coded pulses through the water; an underwater receiver for receiving the transmitted coded pulses, without any physical connection between the transmitter and receiver, the receiver having an underwater piezoelectric transducer, submerged in the water, for receiving the transmitted coded pulses, and a receiver circuit for comparing the received code pulses with stored coded pulses, the receiver circuit including an amplifier for amplifying the received coded pulses, an internal clock generator for generating a clock sign