The ending explained...

Why do we see a blurred figure at the pool?
-to open up a possibility for the sequel
-to satisfy the dumb audience that always needs a happy ending

Why is the figure blurred?
So that intelligent viewers won't think that the ending is absolutely retarded.

Because let's face it - it makes sense that he died on multiple levels. First is the plot wise, his seeking of death (and reunion with his son) since the beginning and his sacrifice for another boy as an absolution for his guilt. And then of course there's the obvious fact that he was shot in the neck with an AK47 after getting hit in the chest by a sniper and then fell of a bridge into a river and sunk to the bottom.