Athlete monitoring using movement sensors can provide important information for coaches and trainers. The main aim of this thesis is to design, implement and test an optical wireless communication link for swimming applications to give real time feedback to the swimmer so that adjustments can be made during swimming. As swimmers are located relatively close to the surface of the water, arm and leg movement can generate a significant number of air bubbles. Total internal reflection from the surface and attenuation due to bubbles is a major problem for communications both below and above the water. For the system the design challenges included: communication type, optical transmitter, bubbles effect, optical receiver, link budget and electronics requirements and optical wavelength. The solution was optical wireless communications in the green spectrum using frequency shift keying (FSK) and on-off keying (OOK). The effect of strong background light was solved using an optical filter on the receiver. This thesis describes a new system to provide a swimmer with real time feedback to adjust stroke rate during swimming. A wrist-mounted accelerometer with a communications link to a receiver located on the goggles allows visual signals to be given to the athlete. As the maximum distance between a swimmer’s wrist and goggles is approximately 1m the communications system must achieve this distance or more. The range varies because of the movement of the swimmer’s arms and head.