It depends on the specific waterbody. In some cases, ownership goes to the middle of the stream and the upland owner owns the bed. In others, the State owns the bed up to OHW. Unless they sold it which the state has done.

In WY, you can float through private property can not stand or anchor. It would be nice if WDFW or some other statewide LE could clearly state the law. That said, you could be right legally and still get run off by an irate and armed landowner.