No, lots spare here. I was standing ankle-deep in water when I took the photo.

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.)

Yes and no. There are loads of shoe shops in town, most of which sells wellies. Most souvenir places won't per se, although neon-colored robust plastic bags which come with ties for securing around ones knees are becoming more common and are the product most marketed for the tourists among foot-protectors. Wellies are really cheap here though because they're so necessary and so widely available. Still, most acqua alta isn't really all that high and can be avoided. S. Marco is the lowest part of the city though, so if it's going to flood anywhere, it'll flood there.