The spatial and temporal correlation function of the sea surface, quantities required in underwater acoustic studies, can be formulated via the surface‐wave energy spectrum. For two spectral functions, proposed by Neumann‐Pierson and by Pierson‐Moskowitz for a fully developed sea, time and space correlation functions are calculated numerically. The latter ones, although functions of two variables, can be constructed from two auxiliary functions, dependent only on correlation distance, when a cosine‐squared law for the directionality of the wave spectrum is assumed. These auxiliary functions are tabulated and plotted. The two spectra produce results that differ only slightly.