No signs of foul play. I suppose it is kind of good news that Achim didn't appear to be a crime victim.
After 2 months, the body was found floating just a mile from where he was last seen. My first thought was that this is odd.
But thinking about it, a body will initially sink in water and Achim's body could have gotten snagged up on the river bottom, ie old tree. Over time, decomposition will make the body buoyant, and in this case, the body may have recently unsnagged from the upward force.
A big thanks to James Villalobos for keeping the story alive.
Rest in peace, Achim.