As we understand more about the optical properties of aquatic substances and their influences on ocean colour, it became possible to envisage the use of ocean-colour data to retrieve information on substances other than phytoplankton, or even to distinguish between some types of phytoplankton under favourable conditions. Ocean colour sensors are being developed with better spectral resolution, improved calibration, and higher signal-to-noise ratio. New algorithms have emerged in parallel, to address the new challenges. There has been a move towards treating the ocean-atmosphere system as a coupled system, and solving simultaneously for oceanic and atmospheric properties; the empirical algorithms for retrieval of aquatic properties are being abandoned in favour of algorithms that are soundly based on theoretical considerations; and new and powerful mathematical and statistical approaches capable of dealing with a multi-variable, non-linear system are being brought to bear on the problem. This report focuses on improving remote sensing of ocean colour in coastal, and other optically-complex, bodies of water. IOCCG sponsoring space agencies Published Refereed Current ocean colour Best Practice