How do you keep ducks out of swiming pool?

I have read on several websites that the only fool proof "repellent" is a dog, one that will go in the pool and chase after them. It must be a dog that will go in the water because ducks are smart and brave and will swim in ther anyway, just avoidin the area where the dog is. I was looking for a way to keep ducks out of our garden pond. Some of those suggestions were any kind of constant movement, i.e.: helium balloons, streamers, scarecrows with flowing clothes. However, this is only a temporary fix also, as ducks quickly figure out there is no real threat and will return anyway. Hope this helps!