Marine Current Turbines Ltd (MCT) proposes the construction and installation of a marine current turbine for the production of electricity in the Narrows area of Strangford Lough, Northern Ireland. Known as SeaGen, this installation will represent the next development step following the successful installation and operation of an earlier turbine off Lynmouth, North Devon, and a significant movement towards the realisation of the World’s first current turbine array for the commercial production of electricity. The report in this series brings up to date previous reports detailing the results of diver and video surveys undertaken in Strangford Lough Narrows, the preferred location for installation of the turbine. It expands upon the marine biological data provided previously, with the results of marine biological and video surveys using diving survey methods, to assess the marine natural heritage at a number of sites within the Narrows. The sites surveyed have included: o Possible turbine sites; and o Areas proposed for the deployment of drilling rigs during site investigation and turbine installation works.