I'm with both rattlinrogue and Nick. I also fish gin clear water and once the sun is up, the topwater bite gets pretty tough. Granted, sometimes, whether it's a moon phase or a frontal condition, they will take a topwater in the sun but not as often or as whole-heartedly as during the conditions r-rogue explained.
I also found , like r-rogue, that if the topwater bite is very good during the sunrise hours, I will shift to the shaded side of the lake after it's up and be able to (usually, I mean, this IS fishing,lol) be able to keep that bite going.