We have deer flies, horseflies, and the most evil of all... those nasty greenhead monsters. The highlight of my summer one year was when I killed a greenhead with a pool noodle. Whenever one starts zooming me, I grab my noodle and they must know what it's for, because they hang back as long as I have that noodle in my hands. However, that's not the most relaxing way to enjoy the pool, so I also keep a grungy baseball cap, and a spray bottle of 30% deet insect repellent in my pool bag. When they start zooming, I spray the cap with deet and keep it on. It works well!