SynopsisInsight in ocean optics has evolved gradually, from centuries ago, the time of mere observations of colour and transparency changes in time and space, to the period starting in the late 20thcentury when satellites were launched and ocean optics became a real science. In other words, an evolution from no more than human fascination for the colour of natural waters to the development of ideas, instrumentation, instrument validation and experimentation, the ingredients necessary to really understand the colouring of water. New challenges within the field of marine optics are designs oninnovative optical sensors for in-situ monitoring of marine environment.This EOS Topical Meeting on Blue Photonics® - Optics in the Sea (Blue Photonics 3), to be held at the Royal Netherlands Institute for Sea Research, Texel, The Netherlands, will provide a major international forum for the discussion of marine optics and its applications. Its aims are to review recent progress in the field, to promote the formation of a community of scientist and engineers working in related areas, and to stimulate the interdisciplinary collaboration required to meet the rapidly developing challenges of the future.TopicsEnvironmental MonitoringCrowdsourcingTopic related Smartphone/iPhone AppsOcean ColourRadiative transfer and modellingMarine bio-optics and remote sensingFluorometryAOP - IOP 2D and 3DUnderwater imagingInnovative sub-sea optical techniques and instrumentation