The protected area is characterized by a vast marsh environment which is indirectly connected to the sea through channels. It extends between the Castiglione della Pescaia and Grosseto areas, adjacent to the Tombolo pine forest. It represents the only remnant of a larger pre-existing wetland area: Lake Prile.
It is a site of significant importance for the stopover, wintering, and nesting of waterfowl. Among the ICBP sites, in recent years, it has been the most important wetland area in Tuscany for wintering waterfowl, and it is also of great importance for the nesting of herons and the western marsh harrier. Among amphibians, there is the Italian crested newt which is an endemic species.