You can pretty much be on any water that you can boat into while the water is at or below the normal high water mark. So if you can boat into an oxbow under normal water conditions, then yes you can hunt or fish it.
Most land on the Arkansas inbetween the levees is corp land and can be hunted. I've ran into one area where there was private land that came up to the river bank. Just watch out for backwater where houses maybe located close to the waterline. Some areas, like lake dardanelle WMA, which is from the lock at dardanelle to the lock at ozark, have a few extra regulations that other pools do not have, but they are outlined in the regulation book.
You can hunt anything 10 yards above high tide. Most banks are marked with white paint at some point marking corps boundary. If you can boat it, hunt it! Some land owners in some places have special exceptions due to old family agreements when the river was damned. But there are not alot of those. Most of they time if you happen to be in one of those spots they will come down and tell you if they have a problem with you hunting there but there are people who will tell you thT it is thier property but it is not. Most of the places with these old agreements are good for geese but not so much for ducks. Good luck.