I’ve watched a guy do it. It is real.
The article says that the Llano River is still flowing. If rivers and streams continue to flow long after it has rained, it's because they are receiving discharge from the ground water. That's proof that there is water down there. Also, the article says the water was in limestone bedrock. Limestone usually has large solution channels which carry large volumes of ground water.
I saw a guy do it with willow. To prove it he had me put vice grips on the branches and it actually twisted in the vice grips at the spot.
We hit water..47 feet and 80 gal recovery.
I wouldnt have believed it if I hand not seen it with my own eyes.