Professor Hunt once asked, “Can you ‘blow’ a whistle under water?” This question was perhaps the first of a series of events that has led to the emergence of a new power-conversion technology for the efficient conversion of hydraulic power to acoustic or vibratory power. This hydroacoustic power-conversion process embodies flow switching techniques that are analogous to switching methods that are employed in electronic dc to ac power-conversion practice. The hydroacoustic technology has been developed for the generation of high-power underwater sound for communication and echo location, and for such industrial uses as high-frequency, rotary-percussion rock drilling and pile driving. The origins of the power conversion technology will be reviewed, analytical models used in predicting equipment performance will be described, and illustrations of specific applications will be shown. Professor Hunt had significant influence on the early phases of the technology development. Illustrations of this influence will be provided and the continuing impact on the program of his general attitudes will be traced.