Doppler sonar is becoming a powerful tool for the remote measurement of the upper ocean water velocity field. Theoretically, precision in the Doppler velocity estimate is limited by the signal to noise ratio of the return, and the ambiguity properties of the transmitted pulse. At fixed signal to noise, the actual precision can be degraded considerably if differences in relative motion of the scatterers in the scattering volume “decorrelate” the return, resulting in Doppler broadening. The return will be significantly decorrelated if scatterers change their relative positions on the order of a wavelength while the transmission is passing through the scattering volume. The limits to peak transmitted power, and typical backscatter strength and ambient noise level in the sea are well known. However, little information exists on the scattering correlation time for typical oceanic conditions. An experiment was conducted from FLIP during June 1977, using a narrow beam 87.5-kHz sonar. Pulses of duration 29–90 ms were transmitted horizontally, at 85-m depth. From the calculated autocorrelation functions, the importance of the relative motion of the scatterers can be determined.