Abstract: A method and device for monitoring and measuring underwater physical therapy or exercise employing fluid elements in either enclosed compressible fluid filled chambers or aquatic exercise devices submerged in water. Measurements are taken via pressure ports formed on first and second opposite surfaces of the hydrodynamic device to provide a pressure differential signal. This pressure differential signal may be compared to a calibrated zero signal to form a measurement signal. The measurement signal is then converted to a digital signal for evaluation by a digital computer. The exercise performed may be stored and evaluated. The arrangement provides information with regard to the type of exercise performed and the degree of exercise performed.