They're called passarelle. I have some good photos from yesterday of them crowded around S. Marco, with the rest of the piazza practically deserted. Acqua alta wasn't quite so high today, even with full moon, without the sirocco - plus it was raining at high tide, so I didn't bother going out again today. (And there was the small matter of having lots of grading to do....)

Cheap, short flights! And it's a much quieter city in winter, as long as you avoid carnevale and Christmas. (You can buy your wellies here if you don't have them to pack.)