The areas regularly submerged by the high tide that are revealed when the sea retreats are called the tidal flats. In Friuli Venezia Giulia, these spread over the sea between the mouth of the Timavo and Grado, while also affecting large areas of the lagoon of Grado and partly that of Marano. The flat and silty section, often covered by extensive seagrasses is linked to the sea by a series of bars or sandy banks that are also submerged by the high tide. In Italy, this is the only coastal area with these characteristics. The fish and waterfowl are highly dependent on the tidal movement with continuous movements of species and individuals that follow the submersion or emersion of the seabed. In general, the fish usually frequent the tidal flats at high tide and then return to the sea or channels when the sea retreats, while the various species of bird alternate depending on the depth, with waders at low tide, herons and ducks surface during intermediate conditions and divers during high tide.