It depends on the lake. For example, at Lake Tenkiller (
http://www.laketenkiller.com/scuba.asp), there is a city underneath. I think that would be neat to explore. There are some others on this board checking into some flooded cities/towns in Tennessee as well.
Lake Travis is a fairly popular diver hangout. Also, I hear understand that Toledo Bend is pretty good. I'm anxious to get back to Houston (few weeks) and try the rigs, Flower Gardens, and the wrecks in the Gulf area. The lakes will suffice when funds are being replenished for the expensive trips.
Richard