Ria-type estuaries correspond to complex systems at the transition between the continental and the marine domains, within a context of rocky coastlines. The Belon Estuary, in South Brittanny (France), is described as a typical ria-type estuary characterised by complex morpho-sedimentological facies, strongly influenced by the South Brittany’s geological framework. The characterisation of the morpho-sedimentological patterns is sourced from recent multi-data acquisition with acoustic remote sensors coupled to ground truth data. The Main Map synthesises the main results of this study concerning the hydro-morphological and sedimentological characterisation of the Belon estuary. This study adds up to former studies over ria-type estuaries and lay out the base for future studies on the hydrodynamic of complex rias, as the Belon estuary.