As tidal turbine deployments continue at test sites and in commercial areas, the potential risk for injury or death of marine mammals from colliding with rotating turbine blades continues to confound efficient consenting (permitting) of devices. Direct observation of collisions is technically very challenging and costly. Estimates of collision risk to date have been derived from complex collision risk models that depend on estimates of the number of marine mammals found in the area. Using a simple collision model, the risk of collision was examined at three real-world sites, each of which featured an indigenous marine mammal. Two different turbine designs were examined at each site to extend the range of the estimates. The results of the model runs allow for comparison of risk at a range of tidal sites for a variety of the marine mammals thought to be at potential risk.