I had a drilled well into limestone shale at 120'. It was artesian and it flowed 20 GPM...I used a dowser to find it. Dowsing is not black magic, it works ! The dowser took a wire coat hanger and cut it into two pieces, minus the hook. Cut that piece into to equal lengths and then bent each piece into an "L" shape, held each piece loosely between the thumb and fingers of opposite hands with the ends pointed away from him and then walked over my land. When the two pieces swayed towards each other. he walked across that spot from another direction; they swayed again at the same place. Drill here he said, you will find water at 100 feet and twenty gallons a minute. Darned if I didn't!.
I tried that same method for a friend on his land...and it worked there too. I dunno why, but it does work!