The Lake Monroe scenario is possible, but it just seems unlikely to me. First of all, I doubt these college students had a boat to use. So they would have to have dropped the body into the water from a road-accesible spot. There are a few spots, but it would take a great degree of effort with little assurance that the body would actually be deep enough/well hidden. Plus, this is occuring around 5am, most likely. There could be fishermen out at that point etc. It seems like too much of a risk and too far of a drive to be worth it.
Lake Griffey seems much more believable to me. You'd still have issues of not having a boat etc, but it is much more convenient from the downtown area, there are several points of unofficial access, and no one really fishes on it/it would be unlikely that you'd see anyone out there that early.
Maybe. Although Griffey is only about 100 acres and about 10 feet deep. I thought I read they did a dive in Griffey. Seems like with a smaller sized lake like that it would be hard to miss a body.