- 2019 Elsevier Ltd In the side-by-side offloading problem, the gap resonance is usually overestimated by the potential theory bas ed methods. This article reviews the up-to-date research on this topic and discusses the existing methods to modify the potential method, in order to obtain a reasonable estimate of the wave elevation. Then a wall damping method is proposed to damp out the wave elevation. This method models the energy loss on the ship hull surface. Thus, a lid is no longer needed. The validity of the method is established through comparisons against the experimental data. Consistent results are obtained for the wave gauge in the middle of the gap. This method is the first step to develop the categories of methods without lid. The motivation is to use the small amount of measured data and a simplified model to generate engineering acceptable results. Given more data, more improvements can be made upon this method and a more general and powerful model can be developed in the future.