Solar energy is the most abundant, sustainable, and environmentally friendly source of energy available on the earth. One promising approach to reducing the reliance on fossil fuels is to generate H2 and O2 by the photocatalytic splitting of water. Whilst there are significant data on inorganic materials that can be used for hydrogen evolution from water and overall water-splitting, there is relatively little information available for organic-based systems. Organic photocatalysts are interesting as they are potentially a very low cost technology, based on earth abundant elements, and more tunable than inorganic systems. There has been a surge of interest recently in light-driven water splitting using organic rather than inorganic photocatalysts. Here, we will examine a range of perylene-based photocatalysis, aiming to link the structures to the activity.