Scattering by roughness of the penetrable water‐sediment interface is regarded as volume scattering and two coupled parabolic equations for outgoing and incoming waves are derived. These equations are solved using a multiple‐forward‐scatter/single‐back‐scatter approximation plus reciprocity. In this way, a novel full‐wave, fully range‐dependent, bottom reverberation model has been developed for long‐range sub‐kilohertz frequency applications. In contrast to all known existing reverberation models, scattering strength is not input as a function of vertical angle. Instead, a statistical model of seafloor roughness is used in which the local power spectrum is input together with range‐dependent geophysical properties of the sediments and basement. The output is reverberation pressure level (RPL) as a function of range, bearing, and frequency. Examples of predicted RPL in the Canary Basin operational area will be shown. [Work supported by ONT.]