Abstract The Orkney Islands and surrounding waters (known as the Pentland Firth and Orkney Waters Strategic Area, PFOW) contain a significant portion of Scotland's tidal and wave energy resource. This paper forms part of a wider study modelling tidal and wave processes, and planned renewable energy extraction, in PFOW using 3D hydrodynamic and spectral wave numerical models. Such hydrodynamic models require a number of spatial data, i.e. high resolution bathymetry, model boundary conditions and measurements for model validation, which are hard to obtain in extreme environments such as PFOW. This paper examines the characteristics and selection criteria of the data used for the development of the models. Most of these data are freely available, and could form part of an open source marine renewable energy hydrodynamic modelling toolbox. In order to include the planned tidal and wave energy developments in the hydrodynamic models of the wider study, realistic tidal and wave device array scenarios are required. However, there is still considerable uncertainty regarding the type of devices that will be deployed and device array layouts. Here, we describe the process undertaken, in consultation with industry, to develop a small number of generic device types and array scenarios for the PFOW, based on insight provided by documentation submitted by developers as part of the Scottish marine licensing process. For tidal developments, an algorithm was developed to determine the site specific array configuration, taking into account the number of turbines, water depth, tidal current direction and the spatial distribution of mean kinetic energy. The wave development sites did not require such detailed site specific placement of devices, and the generic layouts could simply be constructed in most cases without the need for detailed site specific resource characterisation. It is anticipated that the renewable energy industry will be able to adopt our data selection criteria to ensure models developed for environmental impact assessments satisfy the quality requirements of the regulator. Similarly, the methodologies developed for characterising generic device types and array layouts will be useful to academia and government researchers, who do not necessarily have access to detailed device and site specific information.