The time scale of acoustic fluctuations has been found to depend on source speed for a shallow‐receiver shallow‐sound source configuration in deep water off the coast of St. Croix, U. S. Virgin Islands Measurements were made of a 135‐Hz cw source towed at different speeds on a tangential track through a point 7.5 miles from the receiving hydrophones. Higher source speeds consistently gave rise to shorter correlation decay times. As the data integration period was increased from 5 to 100 sec, the measured correlation decay times increased as well, covering the range of 4–462 sec for various source‐speed—receiver‐depth combinations. The position of the receiver with respect to the thermal layer depth also plays a significant role.