Decoys are 3D replicas such as Coyotes, Wolves and the Male White Swan which isn’t a predator but is very territorial and deter the Canadian goose. Some decoy makers build 2D versions with the picture of a coyote on it but these are not as affective and for a little more you can get a 3D model.
It’s best to set up your decoy so that it will sway with the wind. This makes it look more realistic so that the geese don’t figure out your defenses. The price range on decoys varies depending on how life-like they look and their durability. Also remember to look at hunting decoys meant to draw in foxes or coyotes as these are more realistic. Below are some examples of decoys and the links to get them.