being a river guy myself i can say this. if your not sure about the area, ask the owner of the property. you really don't want to deal with cops and what not, even if your in the right its a hassle you don't want or need. simply asking can go a long way.
i was once told by a CO on the pine that although the property owners do not own the river, they can own the land underneath it so if your wading thru the water your still trespassing if your feet are contacting bottom. so unless your in a float tube and your feet are off bottom your trespassing. i don't know how true that is, maybe he was just pulling my leg but this is what i was told.