The Venetian lagoon coastline is constituted by a narrow strip of land, the wholeness of which is vital for the existence of the historical city of Venice and the lagoon itself. Two processes have threatened the littoral zone: the erosive action of the sea and the land subsidence. Because of its particular setting, the fretful state of the littoral zone, is revealed by the negative evolution of the near-shore bottom slope. Five bathymetric surveys carried out in 1954, 1968, 1982, 1988 and 1992 are compared and the phenomenon of land subsidence is then analyzed. Although the latter is not the primary cause of the increase in the bottom slope that has occurred, a certain correlation exists between the two processes. One may say that even a few centimeters of ground surface lowering may actually contribute to the destabilization of the littoral zone. Defense works are being undertaken.