Speaking of the lake, lets try the "choose the possibility" way of theorizing. THIS IS A "This might have happened." THOUGHT LIST.
When a body falls into a large body of water, it sinks. Then when it begins to decompose, it floats. Logic dictates:
If the water is cold enough, decomposition slows down, so a body might not float for several months.
The lake froze over, so if there was a body and it had not yet floated, it would still be down there. This could also be a surprise to the killer should it have been murder
Even if not weighted, if a body were down there, it could be caught on something.
If weighted, it would also stay down.
So, going from those points, if Dylan's body was in the lake, weighted down or possibly caught, he could have:
drowned (either in the lake or elsewhere) by someone and dropped in
been rendered unconscious and dropped in (then drowned as a result)
killed, then dropped in.
fallen in and drowned (while swimming fishing, hanging out, whatever)
fallen in, knocked unconscious and drowned (same as above)
hit their head on something hard enough to kill themselves and fallen in (same as above)
and is caught or still under the ice. Should there be a body and it is eventually found, I have considered the following:
If the backpack is weighted, I think it would not be misadventure but murder (I think no one thinks Dylan would kill himself?). But by whom?
If the backpack is not weighted, it could equally be misadventure or murder.
If the backpack is missing, I would tend toward murder, but it could still be either, being as the backpack might be elsewhere in the lake.
If the backpack is found elsewhere and Dylan is found in the lake, I would think murder, but it depends on how far away elsewhere.
What other reason can anyone come up with where Dylan would be found in the water?
What other scenario would point to Dylan being murdered or accidentally killing himself?