My father was adept at finding water. He did it with two welding rods with the coating removed and then bent at 90 degrees at one end to make a 4 inch "handle". He did it for free and was called out dozens of times to find water for farmers or people who bought a lot or acerage and wanted to know where to drill. I needed to locate a waterline that bisected a three acre lot I owned so a friend that I went to school with came over and used his "witching rods". It took him about two minutes to locate the line. I dug down about 24 inches and bingo, right on top of the plastic water line...
No coincidence, but I don't know the physics associated with it.
carmel