Finite‐difference techniques based on boundary‐fitted coordinates are used to study the interaction of waves with large fixed two‐dimensional structures submerged in water of finite depth. The physical flow field is transformed to the curvilinear coordinate system in which the computational region is rectangular with a fixed square grid regardless of the movement of the free surface. The free surface of the flow is obtained such that the transformation is computed simultaneously with the flow field for each time step. Wave forces and pressure are calculated from the velocity potential of the flow. The comparison of the results for the wave forces of two cases for submerged structures in water of finite depth with solutions obtained by other methods indicates that these finite‐difference techniques can yield accurate results. To demonstrate the usefulness of the numerical approach, the problems of two submerged horizon‐mounted cylinders in different spacings, which do not have classical solutions, are also analyzed.