Money sinks after being wet for fifteen minutes... not sure what the argument here is. R99, do you believe Cooper buried the money?
No. I think the money got there by natural means and that it probably came out of the money bag at the location where it was found. The money bag may have still been attached to Cooper's mortal remains at that point.
Regardless, it is a given that the money bag was moving downhill (from a higher energy state to a lower energy state) at that time and only a flood event would be able to cause this. Thus, Cooper must have been a no-pull who impacted on solid ground several feet higher than the elevation of the location where the money was found. When the flood waters reached Coopers elevation, the money bag and probably what was left of Cooper was dislodged and moved downstream and downhill vertically. After several months on solid ground, neither Cooper nor anything attached to him would have any flotation capability and would move along the bottom of the water.
For the money to end up at Tena Bar, Cooper would have to impact upstream (to the south) and on the west side of the Northwest Lower River Road. This road is built on top of a levee and anything on the east side of it ends up in Vacouver Lake and enters the Columbia River about 15 miles downstream (to the north) of Tena Bar. Things on the west side of the road end up in the Columbia. The river channel between Caterpillar Island and the east bank of the Columbia provides a boundary layer that would prevent anything in the river from washing up on Tena Bar. Any such debris would stay in the main river channel at least until it was past Tena Bar.
Consequently, Cooper was probably a no-pull who impacted on the east bank of Caterpillar Island, or on the east shore of the river channel that separates the island from the mainland. And he would not have entered this channel from the southern tip of Caterpillar Island. So a simple consideration of the geography in the Tena Bar and Caterpillar Island area means that Cooper's impact point can be narrowed down to a very small area.