EyeOnWater is a global citizen science project that helps researchers monitor water quality by collecting observations of water colour and clarity. Using a free smartphone app, participants photograph natural water bodies and classify their colour using the Forel-Ule scale, a scientific method that has been used to study water colour for more than a century.

Water colour can reveal important information about algae, organic matter, sediment and overall ecosystem health. By contributing observations from rivers, lakes, estuaries, coastal waters and the open ocean, participants help scientists track environmental change, validate satellite observations and build long-term datasets that improve our understanding of aquatic ecosystems worldwide.

The project is suitable for anyone with access to natural water, from sailors and paddlers to students, anglers, beachgoers and coastal communities. Every observation adds to a growing global database used by researchers and water managers.