Acqua alta (high water) is a phenomenon which generally takes place in Venice in winter time, when a combination of astronomical tide, strong scirocco wind (warm south-east wind pushing Adriatic waters towards the Venetian Gulf) and seiche (the periodic movement of sea waters, a sort of long wave which washes all Adriatic coasts ) can cause a larger inflow of water into the Venetian Lagoon. Conventionally, in Venice, a sea level higher than 80 cm above the local datum of Punta Salute, is called "acqua alta": at this level height a lot of problems about transport and pedestrian use of roads in lowest sides of the town (St. Mark's Square) arise. When tide gets over 100 cm, the phenomenon involves a bigger part of pedestrian routes. When the tide exceeds 100 cm (5% of public land flooded), the phenomenon begins to affect larger sections of the city. At an altitude of +110 cm, about 12% of the city is affected by flooding. But when you reach the +140 cm, is flooded about 59% of the city. When I took this photo of one of the very many campielli (small squares, literally small fields) the tide had been rising for some hours, but was not exceptionally high, and the boat did not risk to enter the Church. Thanks for your kind comments.