Ten Amazing Mediterranean Cities Slowly Being Lost to the Deep Blue Sea. High tides have flooded Venice, leading Venetians and tourists to wear high boots and use wooden walkways to cross St. Mark’s Square and other areas under water. Flooding is common this time of year and Thursday’s level that reached a peak of 55 inches (140 centimeters) was below the 63 inches (160 centimeters) recorded four years ago in the worst flooding in decades.