Years ago my wife and I use to go to the lake for the day(more than we do now.) We just went swimming and boating,went to boat races ,party cove sometimes etc. We would go all summer. Most every evening we would fish the last hour or two. I would concentrate on places the grass grew to about 8 to 12 ft deep ,on main lake humps,points,ledge drop's from flats into deep water. Sometimes the fish will hang on that edge,but when the water warms a little more than they like they will move out a little deeper and suspend. BUT...in the evening the shad start to feed and the crappie will wake up and start to chase them. They use the grass edges and bottom contours to push them in to to make them easier to catch. Bass and white bass do the same thing. But they can catch them in open water easier...crappie need a little bit of an advantage so they will almost always try to herd them into something to make them break up and turn. These suspended fish you find in summer can be so hard to catch sometimes because they are not actively feeding much of the day. But you find those spots they use to push those fish up at feeding time and then try to be there.Right time,right place,right lure.
Generally...once that water warms to 80 or so you won't find them buried in the shallower grass like you can other times of the year. Unless the lake is just overall shallow . And possibly if the lake oxygen levels drop low in the deeper water for some reason. But they come in to chase those shad.