Have you checked your neighbors gardens to see what thrives? I think for bamboo, your zone is far too cold for it. With some wind, I expect it will have to survive zone 3 as well. In anycase, some bamboos clump and are well behaved. But others are a nightmare that sends out rhizomes far from it's original source and these types require 2 feet deep root barriers to contain them. You don't want to deal with these horrors.

These is a link to salt tolerant plants http://www.ext.vt.edu/pubs/trees/430-031/430-031.html. YOu can see there are plenty available. However it doesn't say whether they are good in wetland conditions. This is why I suggested that the best way to find out what works is to tour your neighborhood to see what thrives.

Ianna

If you are not near underground piping or wells, I would try willows. They love wet conditions and grow quickly. Plant them close together for privacy. There are different kinds too. A hedge of curly willow would look cool! Also you can just poke a willow stick in the ground and it will root and grow. So take a few dozen cuttings form one you find, with the owners permission of course, and then stick them in the ground for your hedge. Keep them damp until they root and start growing.

I don't know if they will survive the salt, however, but it wouldn't cost you anything to try, if done from cuttings.

Weeping willows and curly willows are far more problematic when compared with bamboos. Bamboos can travel far from it's original site but at least it won't destroy foundations or sidewalks. In contrast, willows will do that. So my opinion is that this is not a good hedging plant. In fact, I haven't seen it used as hedging plants elsewhere. Except for one innovative idea in Britain where they created temporary living fences, criss crossing willow sticks and also created wig wams. A fun summer project.

Now there are smaller screening varieties (zone 6 stuff) that aren't invasives. Again these are not hedging materials but can be used as screening shrubs.

My honest opinion.

ianna