I can understand not allowing untrained people in the caves, but I’m not a big fan of restrictions on bodies of water. I prefer information and warnings to closings and restrictions. It’s a slippery slope, first they might close it to certain classes of people, later to everyone.
In the case of eagle’s nest for instance, as a swimmer I would love to swim around the basin and admire both the scenery and the cave divers, and perhaps provide some support to people who are really cave divers. As a shallow free diver I might enjoy diving in the basin but never going into the chimney. You don’t have to be a rocket scientist to see that the tube penetration would be incredibly dangerous, and if you don’t realize that a warning sign should be sufficient. If we make a law every time fools do something dangerous we are letting fools determine everyone’s rules.