We welcome Sheppard’s comments on our recent assessment of both ecological and geomorphic change at Diego Garcia Atoll in the central Indian Ocean [1]. Whilst our assessment incorporated numerous aspects of change, including movements of the lagoon rim shorelines, changes in the terrestrial vegetation on the lagoon rim and amendments to the bathymetry of the lagoon basin through dredging activities [2], this comment solely addresses the estimates of shoreline change. Here we make some brief remarks relating to this shoreline assessment of Diego Garcia and elaborate on some of the complexities of the geomorphic processes that underpin shoreline dynamics. These complexities have important implications for understanding reef island shoreline dynamics, both at this site and globally.