To elucidate the effects of elasticity the hydrodynamic impact of a 2-D flat-bottom shell box onto a water surface was investigated in detail using the finite element code Dytran. An ALE coupling algorithm was employed to handle the interactions between the box and the fluids. In this study, both air and water were treated as compressible fluids and their properities were modeled through the equation of states. Calculated results show that the air cushion plays a very important role buffering the impinging. Under the deformed concave bottom an air cushion layer will be easier to form up. For high impact speed, the pressure for the elastic box is much lower than that for the rigid box. Excited by the impact, the impinging box oscillates with about its natural frequency.