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There is a growing need for voice communications underwater between divers and between divers and surface vessels. This paper discusses the general problem in terms of system analysis. The authors decided to direct their efforts toward the low-cost, volume market of the sport and commercial diver. A communicator for this purpose must be simple, reliable, and low in cost. Hydrotalk, the result of their development, radiates an omnidirectional, audio acoustical wave through the water medium. Reception is accomplished by the listening diver's unaided ear. A large part of the development involved the creation of an improved underwater transducer, having a high coefficient of coupling between its signal input current and the sound power produced in the water. While this device represents a real step forward in solving the underwater communications problem, the authors are aware that more work needs to be done in improving intelligibility of the voice signal input to the microphone. This will probably be in the direction of a simple and safe full-face diving mask, which will provide a common chamber for the nose and mouth in which to mount the microphone. The authors are continuing their development work along these lines.