Another slowly varying wave force or moment occurs as a result of wave diffraction and reflection about the floating vessel. This is a potential flow effect that is independent of viscosity. For a moored ship or platform in a current, there can be low frequency surge-sway-yaw motions generated as a result of large-scale vorticity in the wake. This is not unlike the vortex-induced oscillation of cylindrical bodies such as pilings, cables or pipes in a current