that siren. [ humming siren ] it is the sound of an approaching aqua alta, high water propelled by moon and wind. you see a full moon brings higher tides, and when the sirocco winds are blowing up the back of the italian boot, adriatic seawater comes rushing through the three inlets of the venice lagoon. it s predictable, so three hours before the liquid lifts comes that haunting alarm. one tone means the water will reach 110 centimeters above normal. two tones, 120 and so on. today it will top 130, 4 3 above normal. higher parts of the city will stay dry, but here in san marco 130 is just enough to render your wellies worthless. i don t know why i bothered to put on the boots. woo, that s cold.