When a body is put into waves, the waves are scattered by the body. If there is another body in the near field, the body is affected by the scattered waves and the hydrodynamic forces on the body are sometimes quite different from those on a single body. In this paper, by actively making use of these hydrodynamic interaction effects among bodies, we optimize the arrangements of the bodies in the sense that the hydrodynamic forces on the bodies are minimized. It is shown that this can be achieved by combining the existing hydrodynamic interaction theory and the nonlinear programming techniques. Through several example problems the effectiveness of the present method is demonstrated.