The research aims at investigating the stability of offshore monopile scour protection under wave and current conditions. Both small and large scale experiments will be employed in this research in order to quantify more accurately the effect of scale effects on the prediction (and design) of the stability of offshore monopile scour protection. The data analysis of the two differently scaled model reveals strong model effects and scale effects in this type of hydraulic experiments. This emphasizes the limits of applying existing design methodologies to large scale models and prototypes.