In this work, the response of a single-degree-of-freedom and a multidegree-of-freedom system subjected to wave loads given by Morison’s equation is obtained in two different ways. One is a direct integration in time using the constant-average-acceleration method. The other is the Hybrid-frequency-time-domain method is that the equations of motion can be solved directly in their nonlinear form. The frequency domain solution can be obtained only after the equations of motion are linearized. To solve a nonlinear problem, it is thus necessary to apply an iterative scheme..