Though the self‐reciprocity technique provides a simple means of obtaining absolute calibrations of electroacoustic transducers, it does not seem to have found wide acceptance. While the acoustic impedance of water and air differ sufficiently to make the loss of acoustic energy through a water‐air interface negligible, the ocean surfaces is generally not a plane, and hence, would not seem to be a suitable reflector for use with the self‐reciprocity technique. However, by using the mean of the returns from a number of pulses, it is possible to use the ocean surface. The accuracy of the technique is a function of the number of pulses, and possibly, variations in wind and sea conditions. With this technique one can make free‐field calibrations of large, low‐frequency transducers at high hydrostatic pressures and determine any variation as a function of pressure.