There are several areas of the lake that are deeper at the edge. If you look on Google maps you can see this. Also, while it is possible this reservoir is shallow all the way around, I have never seen another reservoir that is shallow all the way around. There have always been shallow areas, and deep areas close to the shores of all the ones I have been to (somewhere in excess of a hundred).
I also don't understand how you write "if you put a body into a lake from shore it's not going to magically move itself into deep(er) water" then write "Sunken objects will be moved by the current and end up at the dam" Those seem to contradict each other, so could you explain?
Also, there is so much flotsam and jetsam on the bottom of a reservoir, anything that sank in it can get caught on something, or caught under something, and maybe never move again, or maybe, with the advent of a storm or watercraft movement, get stirred up and move along or float to the top.