Growing up I helped my dads cousin relocate a well. Used 2 wire rods, bent at 90*. We were able to find several spots and get the depth that the water was at. Struck water on the first try, within 5' of what it was said when dousing.
Now, if I can just remember how it was done. I remember when the wires crossed, that was the location, then there was something else to get the depth.
In the show "Off the Grid" with Les Stroud, they did dousing with a willow branch.