The main limitation of the development of underwater wireless electromagnetic communication is severe attenuation introduced by the seawater characteristics of high permittivity and high conductivity. Fortunately, in previous studies, it was found through experiments that the loss between two underwater antennas near seawater surface or seabed is much smaller than the higher order severe attenuation for the line of sight (LOS) path in seawater. But no one has given reasonable explanation for this phenomenon. To solve this problem, we investigate the propagation mechanism of this phenomenon theoretically. The main component of seabed-rock-layer is basalt, an alternative seabed-rock-layer communication channel model based on evanescent wave generated by the total reflection on the seabed-rock-layer surface is proposed in this paper. Then we analyze the performance of this model according to Goos-Hanchen (GH) Shift of evanescent wave. Simulation results show that the path loss in this model is about 1/20 of that in seawater and the propagation velocity can be increased 20 times. Proposed technology is expected to become an important part of underwater high speed and reliable communication.