A prototype swimming tachometer is described which consists of a waterproof box housing a battery-powered electronic system linked externally to an opto-electronic velocity transducer. The device is strapped to the hips, where it monitors water flow to produce continuous measurements of two critical variables of swimming performance, namely, velocity and acceleration. These measurements are converted in real time to auditory feedback signals to the subject via an ear plug. Permanent records may be taken simultaneously as an option using a switched external line.