An imaging sonar in very shallow water environments faces significant challenges in accurately detecting underwater small targets due to the adverse effects of dense multipath propagation and strong interface reverberations. To accurately characterize the interface reverberation characteristics of imaging sonar under moving platform conditions in very shallow water, an interface reverberation model incorporating both sea surface and seabed reverberation is established. This model integrates physical processes such as the acoustic propagation in very shallow water, sea bottom and surface scattering, and sonar platform motion. Ray theory is employed to calculate high-frequency acoustic propagation, while unit scattering and the small slope approximation (SSA) are used to compute sea bottom and surface scattering. Taking water depth, platform speed, imaging range, and vertical beamwidth as inputs, the model yields the statistical characteristics of reverberation under dense multipath conditions in very shallow water. Results from numerical simulations and experimental data analyses indicate that the statistical characteristics of the envelope of interface reverberation in very shallow water are primarily influenced by water depth, imaging range, and vertical beamwidth. The presence of dense multipaths in the very shallow water causes the interface reverberation envelope to tend towards the Rayleigh distribution and enhances the temporal correlation of the reverberation through superposition of dense multipaths. Platform speed has little impact on the statistical characteristics of the reverberation except for the Doppler shift caused by relative motion. Furthermore, as the imaging range increases, the multipath components in interface reverberations become richer, causing the envelope to conform more closely to the Rayleigh distribution. Additionally, as the vertical beamwidth increases, the interface reverberation envelope gradually transitions from the K-distribution to the Rayleigh distribution.