This thesis is about the beginning of a global tide model in DFlow-FM, a project by Deltares. The first focus lay on finding the best grid that can be used for this model. We tried to grids, a rotated lat-lon grid and a squarely grid with local refinement. After calculating the RMS-value it was found that the local refined grid gave the best results and should therefore be used. The second part of the thesis was about internal tide, how it should be included in the model. This needs future work to improve the results but the way it should be included was found to be a linear friction coefficient.