The problem with shooting geese over water, or as they leave or come back near the water, is that they will make a decision to leave the area permanently. If you try to identify a field they are going into and either lie down there well hidden, or spot some ambush site where you can take them coming in to the field or leaving it, then once you do spook them all they will do is switch to another field in subsequent days, so you can have some more chances, and others will still have hunts as well.