Marine renewable energy generation (ocean energy) is a growing industry due to global demands for increasing power supplies and reduction in carbon emissions. Intrinsic assets associated with deployment environments and values associated with their existing use need to be established to ensure balanced decisions can be made regarding the sustainable development of marine areas. This paper assesses the value of the marine environment around St. David's, Pembrokeshire, UK, where a tidal stream turbine demonstration project is underway and larger array developments, both wave and tidal, are planned for the next few years. It was found that the marine environment contributed, on average, to 78% of visitors' total enjoyment of the area. A Contingent Valuation Method (CVM) and Travel Cost Method (TCM) used data collected from questionnaires at the case study site to produce cost and valuation results. The results showed there was a higher revealed preference average value of 148 pound per person attributed to the area through the Travel Costs incurred by visitors than their stated preference average valuation of 6.70 pound per person from a willingness to pay CVM contribution. Interviewees were also asked about the potential impact renewable energy generation in the area would have on their visit. Visual aspects of developments and the impact of wave height reduction were queried in particular. Using these responses from interviewees, the influence of marine energy generation in the case study area and the impact on the value of the marine environment was analysed. The results show that only a small number of visitors, 3.5%, would be put off visiting the area again due to marine renewable energy developments. Underwater, non-visible devices were shown to have the least impact on people's enjoyment of the marine environment compared to surface based designs. These results suggest that marine energy developments should not affect tourist revenue.