Abstract: [Objectives] To simulate the complex nonlinear interactions between the free surface and instantaneous wetted hull surface during ship navigation, an automatic mesh generation method is proposed. [Methods] The method takes a whole-hull triangular mesh file as input and automatically generates meshes for the instantaneously transforming free surface and wetted hull surface. It has the capability of handling arbitrary hullforms with complex bow and stern geometries while exhibiting strong robustness. Simulations of waves generated by the KCS hull at various speeds are conducted using the proposed method. [Results] The predicted ship-side wave profiles, wave patterns around the hull, and wave-making resistance agree well with experimental results. Moreover, at higher speeds, the simulated wave surface at the KCS stern consistently stays below the transom, exhibiting a dry transom characteristic. [Conclusions] The results demonstrate that the proposed method can accurately model nonlinear ship waves and has the potential to simulate the flow field around transom-stern ships.