Chip - Try rosy reds if you can find them. They will hold up in hot water better than shiners. I can't help you with Occoquan-specific suggestions, but questions about fishing depth have several answers, including:
- fish rise to the surface early and late in the day when the sun is low in the sky.
- crappie strike from below, so always err on the side of 12" too shallow.
- if the lake is deep enough to have a thermocline during the heat of the summer, base your fishing depth on the depth of the thermocline, not bottom of the lake.
- otherwise, fish about 2" above the bottom during the heat of summer.