This research aims to develop a flexible, simple, low-cost, robust, deployable sensor with anti- fouling measures to detect colour change in marine environments. Such a sensor could be used to detect events, inform sampling regimes in coastal areas and act as a qualitative decision support tool. This is useful to decision makers in cities, coastal areas and globally and as gathering data can be expensive using commercial instruments a low cost sensor enables more data to be collected with a better spatial range and resolution. Detecting colour change in water could give warning of events like green tides, e.g. (right) in QuingDao, China, often caused by cyanobacteria.