To support and improve the evaluation of the test results of wave energy and tidal energy generators, it is important to understand the detailed physical conditions at the test sites. EMEC has chosen DHI’s MIKE modelling technologies for studying water levels, currents and waves at their test sites. DHI has assisted EMEC in constructing numerical hydrodynamic and wave models of the Orkney Islands using the flexible mesh version of MIKE 21. This model permits spatial varying resolution, so that the complex tidal channels and local topographic features that may influence the tidal and wave dynamics can be sufficiently resolved. This paper highlights the modelling activities for EMEC’s two test sites.