As someone mentioned earlier, Sills made a comment that they had a great video shot of the Dermond's dock, but not 'the area in question' (great post Hickory Born!!!!).
If you take a look at the pictures from the link above, there are a couple things that stand out.
1) The crime scene van is parked and open right near the garage, even though there is enough driveway space it could be almost anywhere else in the front of the house.
2) If you are facing the house from the dock, the right of the property is heavily wooded, obscuring a view of almost anything.
3) I would suspect if one walked straight thru that wooded area, they would arrive right at the back of the Dermond's garage.
Now I'm curious about two things:
How shallow is the water in the area along the property line behind the garage?
(Our cabins are in the New England so I don't know much about Georgia lakes. But where we are, there are areas that have heavy underwater tree roots and rocks near the dock area, but other areas that property owners specifically clean out for swimming, hence, no obstruction for a shallow bottom smaller boat)
Is there a door at the very back of the garage? If so, is it facing into the backyard, or straight at the very back toward the lake?