I was on vacation.
For tubing/boating, it doesn't matter if it's navigable or not. The Commonwealth owns all flowing waters. And there's a public easement to float any water.
That said, if it's not navigable, boaters can't fish, stop and linger, stick their feet through and touch bottom, etc. Float through and that's it. Theoretically maybe their boat can't even scrape bottom. Because the streambed is private even if the water flowing over top is not.
Navigable means the public not only owns the water, but the streambed as well. Up to the low water mark with an easement in favor of the public to the high water mark. Public highway. Fishing allowed and any other legal activity. Just can't get out of the channel onto the floodplain.
The LJR is navigable and the issue is decided by courts. Done deal. Many other waters are also likely navigable. Have been declared as such by state legislature. 100s of them. But the state legislature declarations carry no legal water. Each waterway has to have it's day in court, and most haven't, but the LJR has. Meaning Spring, Penn's, Elk, Pine, Big Fishing, etc, are among those with state legislature declarations of public highway but no court date. The public has as much claim as landowners. If there's an issue it goes to court, a judge decides who was right, and punishes whoever was wrong retroactively, so trespass at your own risk but posters are at their own risk as well. Those declarations usually mean it was once used for commerce, and serve as evidence of such. The court definition of navigable is whether it CAN be used for commerce. If it once was, well, then most reasonable judges would conclude it can. But you never know with judges.