Flies have a pair of "complex" eyes that is composed of thousands of "simple" eyes. This provides them with a mosaic view. Light refraction causes confusion to the fly.
The only way this will work for you is if you put some form of a repellent for them in the water that will draw them to it otherwise you will be fighting a losing battle and get frustrated with it. Try doing a web search for this and it will give you all of the details that you need.
