I want to throw this out there for speculation. I have offered some thoughts on this, but I want to get others.
If we assume that the Columbia River was the mechanism that delivered the money to the beach on Tena Bar (I know that's a hard no for a few of you), what would be your best guesses as to how that happened? Did it roll along the bottom and get dredged up? Did it float on a piece of river debris or vegetation? Cooper's corpse? You have to keep in mind the diatom study of course.
Would love to hear some informed speculation about how the river might have delivered the Cooper cash to Tena Bar.
I think dredging has been dismissed as a possibility. And non-natural causes can be dismissed also.
The money had to be moving downhill when it arrived at the location where it was found. It could not have come from the normal river channel. Consequently, the money had to be moved by a flood or high water event from where it had spent some time on dry land to where it was buried. This means that the money was initially at a higher level than the normal river channel water level and probably still in the original money bag and tied to Cooper's body.
Eventually, a high water event raised the river level until Cooper's body, and attachments, was displaced and moved downstream and downhill from their original location. Cooper's body, the unopened parachutes, and the money bag would not have any buoyancy after being exposed to the local Tina Bar environment for a very short time. These items would essentially be dragging along under water until they were snagged at the money find location. The money bag was probably damaged during Cooper's no-pull impact and several bundles came out of it when it snagged. After a brief time, Cooper's body and ever thing else continued on downstream and were never located.
Some skeletal portions of Cooper or his attachments may have remained in the original impact location. The Tina Bar area has some man eating brush and anything that ends up in that brush is going to still be there.