One thing that many anglers forget is that during the peak of summer, the forage base of almost all bodies of water is at its peak. You are competing with the buffet that the fish have to choose from. They will more easily ignore a sloppy presentation or an offering that looks out of place, unlike during their spring or fall movements. The other behavior that is often overlooked is that during those peak summer months, a good majority of the fish will have set feeding periods (not by a human's clock, but by theirs) and they know where to feed and what to feed on at those times.
That's the downside. The upside is they also tend to group together more during the summer, whether feeding or not. Did you ever have a summer outing when you caught 20-30 bass in a relatively short period? Yes, to many of the fish that use the shallows as their home this doesn't apply, but I'm talking the majority.
Now take just those few facts and apply them to a small body of water like a pond and you can see why it can be very frustrating when fishing them during the summer. The odds are stacked against you, but then again, there's always that one memorable outing that awaits you too.