Existing methods to compute wave motions of and loads on ships either neglect effects depending non-linearly on wave height (linear oundary-element methods), or they take too much preparation and computing time for most practical applications (field methods solving Euler or RANS equations), or they take into account only some, but not all substantial non-linear effects (non-linear potential methods), or they are suitable only for strongly simplified hull shapes like Wigley ships. Here a potential method is described which avoids the listed deficiencies of existingotential methods while being much faster than field methods. Many new or seldom-applied features were required to attain that goal. To list here only a few of them: Instead of resolving splashes and wave breaking at the waterline, emphasis is laid on avoiding instabilities while skipping these flow details. The total flow potential is added from that of the undisturbed wave and the disturbance; this allows damping of the latter to avoid wave reflections at the outer boundary while leaving the incoming wave unaffected. Time derivatives of the potential φ are determined by computing both φ and φ̇ from the respective boundary conditions. The method is verified by comparisons with model experiments and different kinds of computations.
