The measurement of solar UV under water is not a simple process. In the underwater environment the difficulty of obtaining useable data is greatly amplified due to the optically complicated and at times unpredictable nature of water itself. The following practical exercise designed for use in the Year 11 and Year 12 Physics classroom aims to provide students with a practical understanding of how the Beer-Lambert-Bouguer Law can be applied in an underwater environment and how handheld solar UV measurement instrumentation can be employed in conjunction with the Beer-Lambert-Bouguer Law to accurately measure the optical properties of water. (Contains 5 figures.)