Estuaries serve as a meeting point between land and sea. Estuarine hydrodynamics are very complex because there are interactions between different water bodies: the sea with the same phenomena as the coast ocean (tides, waves, surges, sea level rise) but also the river, its tributaries, and groundwater. Numerical models have been increasingly used to predict river and estuarine flow, water quality and sediment and contaminant transport processes. However, to better define these models, and also to assimilate data into those models, one needs data, but only a few estuaries in the world have enough in situ gauges to allow this. The interest of using satellite height data for estuaries is to provide information on the hydrodynamic spatial variability. Until now, within estuaries, the contribution of satellites has mainly focused on the monitoring of water color and its relation to suspended sediment and chlorophyll. However, e.g. turbidity distribution varies considerably with tidal and river flow conditions, fluctuating on a variety of timescales, and are heavily influenced by bottom topography. In order to validate these models,  we need the high resolution, 2D satellite altimetry data which Swot is bringing.