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 the imaging sonar under moving platform conditions in the very shallow water, an interface reverberation model incorporating both the sea surface and the seabed reverberation was established. This model integrates physical processes such as the acoustic propagation in the very shallow water, the sea bottom and surface scattering, and the sonar platform motion. Ray theory is employed to calculate the high-frequency acoustic propagation, while the unit scattering and the small slope approximation (SSA) are used to compute the sea bottom and surface scattering processes. Taking the water depth, the platform speed, the imaging range, and the vertical beamwidth as inputs, the model yields the statistical characteristics of the reverberation under the dense multipath conditions in the very shallow water. Results from numerical simulations and experimental data analyses indicate that the statistical characteristics of the envelope of the interface reverberation in very shallow water are primarily influenced by the water depth, the imaging range, and the 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. And the platform speed has little impact on the statistical characteristics of the reverberation except for the Doppler shift caused by the relative motion. Furthermore, as the imaging range increases, the multipath components in interface reverberations become richer, causing the interface reverberation 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.