It's only supposed to be a temporary measure until something more long term is devised – and the walls and pumps can stop up to 1.1 metres of water, something MOSE isn't optimised to do yet.
But it seems to be not impossible in this case that one day somebody might just turn up an inscription of Tut Mose II, year 25, in which case textbooks have to be changed.
Mose is made up of seventy-eight hinged steel floodgates that run for 1.6 kilometres along the sea floor beneath the three inlets to the Venetian Lagoon.