Sounds reasonable. I've had a similar experience.
Fished a pond filled with large bluegill/redear with my grandfather while growing up. Water was shallow and very clear. We would sneak in really quiet and sit behind willow trees for 10 minutes or so before fishing. If we stayed hidden the biting was good. If we got out in the open or stood up by the tree, the fish would move out a litte further in the water and would not bite.