An underwater acoustic surface‐reflection channel is treated as a linear random time‐varying filter. Thus complete characterization of the channel reduces to a statistical description of its stochastic system functions. This paper presents the results of measurements made in a model tank with a wind‐driven surface in terms of the channel impulse response, transfer function, bifrequency function, and their ensemble averages. The impulse response is taken as the primitive because it permits evaluation of the transfer and bifrequency functions without need to resort to multiple measurements at different frequencies. Both the time‐ and frequency‐spreading characteristics of the channel are clearly evident in the system function data. It is shown that, given a single set of impulse response measurements for each geometrical configuration of interest, it is an easy matter to study the frequency response and frequency‐spreading behavior of the channel over the bandwidth of the acoustic pulse. The impulse response itself, of course, yields the time‐spreading behavior of the channel directly. Furthermore, favorable comparisons are made between impulse response derived data, and data obtained by single‐frequency measurement techniques.