The ESAQS project (Ecological Status of AQuatic systems with Sentinel satellites) intends to develop and validate algorithms to get ecological indicators in inland and coastal waters with the new generation of European Earth Observation satellites: Sentinel-2 and Sentinel-3. The combined use of these satellites, together with NASA Landsat-8, will allow the simultaneous monitoring of a large number of water bodies, with an unprecedented spatial resolution (up to 10 m) and a weekly frequency. ESAQS aims are to provide tools that will help both water authorities and scientists to keep a synoptic record of ecological status at river basin scale, to detect phytoplankton blooms on a timely manner as well as mapping surface processes linked to hydrodynamics in a very fine detail. The obtained algorithms will be based on physical modelling of the sunlight and water interactions. They will be calibrated and validated with in situ data obtained during a three-year campaign on a diverse set of water bodies in Valencia region (East of Spain), covering a wide range of trophic states. Chlorophyll-a concentration, as indicator of phytoplankton biomass, Colored Dissolved Organic Matter (CDOM) and suspended solids are the three key variables, along with phycocyanin concentration (marker for Cyanobacteria) and water transparency to determine water ecological status. During the first months of ESAQS project, the field campaigns have been centered in the shallow hypertrophic Albufera of Valencia, for which a specific method for Chl-a has been successfully validated. The obtained thematic maps give insight of the phytoplankton distribution patterns with a resolution never attained before with operational satellites and help interpret the lake hydrodynamics.