CFD - or finite-element-type simulations of the three-dimensional non-linear evolution of ocean and coastal waves are still widely impractical on today’s high performance computers because of the complexity of the underlying equations. Common simplifying assumptions lead us to have to solve Laplace equation with boundary conditions at the free surface. For reasons of computational efficiency, we propose to solve the latter with a high-order spectral model (HOSM) to accurately simulate relevant processes within an acceptable amount of computing time. We are going to present an MPI parallel HOSM that is capable of simulating non-linear wave interaction and effects that originate from a non-trivial bathymetry profile. In its current optimized version, the global communications needed for the fast Fourier transforms (FFTs) is a major limiting factor. We are going to discuss recent computational improvements that we have undertaken in order to reduce runtime and increase efficiency as well as extend the applicability of the model beyond the simulation of random ocean spectra in periodic domains.