I checked Bert's wt and it stated: . . . . . . . . . . . . . . . . . . . Wait until one of the dogs is passing by. Quickly throw the swimming duck over the dog.
I don't have the game and have not played it yet. I gather from the wt that you have to check the dogs first (get attacked), get the duck and then come back.
Maybe the picture of where the dogs and duck will help - check Part 6 of Conspiracies might help position yourself.