Multi-element profiles have been used for decades to assist aircraft during landing and take-off by significantly increasing lift during these vital stages of operation. This paper presents the preliminary Computational Fluid Dynamic results used to validate and optimise the design of a multi-element profile for a vertical-axis tidal stream energy device, where the relative velocities, fluid type and Reynolds number differ significantly from that found in the aerospace sector. The resulting designs and optimisation have allowed for the manufacture of stereolithography prototypes for in situ testing in the 'wet' facilities at Lancaster University. A vertical-axis device has been selected as it offers significant advantages in shallower tidal water, often found near shore, thus reducing the required infrastructure and set up costs associated with the deployment of new technologies. The UK is in a prime position to exploit energy capture from tidal stream with the advantage over other renewable sources in that it is completely predictable. Such exploitation requires the quick turnaround offered through design, analysis and product development technologies.