Well to help yopu any duck that lands on the water after you shot - simply swat. No problem with that at all.
One thing is be carefull with your shots and use the wind on the pond to help you. Yo are doing the best if you are using a fishing rod and the treble hook need not be sharp and you can remove the barbs.
The other thing to use is waders and only hunt water you can wade easily to retrieve your downed game.
This is a very ethical question and I hope others have some better ideas for you.
JW