This paper presents results from research which aims to establish better understanding of the shear resistance of rock-steel interfaces to develop enhanced gravity foundations for tidal energy generators. Findings from laboratory testing are presented along with issues arising from field visits at sites with high tidal energy potential in Scotland. Direct shear box tests were carried out on rock analogue-steel interfaces at relatively low normal stresses. Different rock analogues and various techniques (polishing, machining etc.) were used for the surface preparation of steel samples resulting in a wide range of rock-steel relative interface roughness. This allowed the investigation of the effect of surface roughness on the interface behaviour along with the effect of the rock's unconfined compressive strength. Results of laboratory testing suggest that relative rock-foundation roughness and rock strength are significant controls on interface resistance.