A lot of times, especially when it's cold, geese like to roost in the water. If your're seeing all these geese on the river in the evening and they stay over night, I would be careful and try not too hunt to close to the roost. Their roost is kind of like your home. They fly out to cornfields or whatever to eat, if they get shot out of a cornfield they will just move to the next one. Kind of like your eating establishments. If you go to Burger King and Burger King burns down. You will just move to Mcdonalds. But if your home burns down (geese get shot at around their roost). Then youre screwed, youre going to have to move to a whole new area anf find a new home. Your result is no more geese. Thats one thing you have to be careful of on the water.
Secondly, if you can find a place where the geese like to feed, say on a river bend out of the wind. Concentrate on those spots. If they fly out of the river at a certain spot, go to the spot and get a pass shot or maybe they will come by and take a second look and you will get a little in your face action.
Good Luck