The Lagoon, an unusual natural formation, was caused by the overflowing of the Piave river in 1935, whose bed was modified in its last stretch after a large flood. The Lagoon stretches between the Eraclea's Lido and the mouth of the Piave river and it is a sea-lagoon, being supplied with water only by the flood-tides. Still uncontaminated, the Mort is characterized by shallow and calm waters with a sandy and muddy seabed, rich in phytoplankton.