I think it depends how far you need to go in the water to get to the spot where you are going to hunt. If you can walk to your spot fairly easily, you can find some instructions on how to build a nice floating blind from 2 pieces of plywood and a small structure.

If you have a ways to go, a boat is a very nice thing to have. It opens up a lot of possibilities that you wouldn't normally have.

If you're going to hunt sea ducks, I think a boat is a necessity.

Good luck.