Based on our highly efficient Navier-Stokes solver, LVOF (Li, et al., 2004, 2007), we present some results for water entry and exit in a 3D numerical wave tank, by implementing our design of a mass-force coupling scheme for water impact (Li, et al., 2007a). LVOF is constructed by a novel VOF finite volume cut-cells approach that incorporates surface tension, coupled with a dynamic subgrid-scale model. Our mass-force coupling model in theory represents the coupling of a moving body on the flow, which is realized through introducing the internal source function. Importantly, a solid body is treated as a fluid, especially the solid-liquid phase front is captured over a fixed Cartesian grid without smearing the information at the particle-fluid interface. Grid refinement studies are performed for test problems involving the wedge entry and exit. In addition, issue about the convergence performance is addressed under the prescribed entry velocity. Very encouragingly, the results agree with measurements available. It is demonstrated that most of typical features in complex flow patterns can be captured in waves caused by impact, by using LVOF.