I've only heard of poeple doing this in fields. Doing it over open water sounds dangerous and expensive.
Look into flu-flu arrows. They have big gay looking fletching like in cartoons. This slows the arrow so it dosent go as far and makes arrows retrievable.
Found a pic for you. Yes they look slightly homosexual but unless you can afford a couple dozen arrows every time you go out this is what you need. Bright fletching makes finding them easier.
I would find a small patch of flooded field, some place where you know where the ducks are going to try and land. Puddle ducks are also slower and possible to hit. If you can knock down fast ducks with a bow you should be shooting in competitions and making lots of money.
Good luck, i'll stick with my shotgun