Answer:

There are several solutions that can work. There are even repelents that are designed to keep ducks away. There are several available online. However, there are easier solutions as well. Floating bright colored toys, feeders, etc. are known to keep ducks away. Ducks also do not like bright shiny items. You can wrap some small items in foil wrap (shiny side out) and place around the pool. I have heard bricks work well for this. Even strategically placed sun catchers could do the trick.