An intensive data collection campaign has been conducted in the coastal waters of the southern North Sea during which a variety of marine optical parameters have been measured together with water quality parameters. A suite of semi-empirical ocean colour algorithms to derive the main constituents of Case 2 waters has been developed for the area and these have multi-temporal applicability. Such algorithms have been tested on airborne reflectance data collected using the CASI (Compact Airborne Spectral Imager). An investigation into the relationships between the inherent and apparent optical parameters has been carried out and various models from the literature have been tested on in situ data. New coefficients in the reflectance model are proposed for coastal waters. An empirical relationship between subsurface and above water reflectance has been defined and the angular distribution factor of spectral radiance (Q factor) calculated. A value of ir for Q is recommended for coastal waters which is in contrast to the value of 5 proposed by other researchers. The understanding developed within this study of the optical properties of coastal waters will enable maximum potential to be made of aircraft and satellite remote sensing.