I have done it twice with bent coat hangers and it works and is a cool party trick to boot! However it’s just getting magnetic effects from small current flowing through underground metal pipes. Actually finding deep underground water in pure dirt? – that one I’m not sure about.
But I gotta say the “divining” freaked me out at first it was like Holy S(&#* this really works. But like I said it was for metal pipes and that one I can rely on my college electromagnetics course to say there is a real reason for it other than some spiritual thing. Though if I would have been a better salesman I could have pretended to go with the “spiritual” aspect of it.
Actually I haven’t thought about this in over 20 years when I did that. Now that I’m older instead of being more skeptical, I’m actually analyzing it more and I think yeah, it definitely might work in some situations. Even without a metal pipe (which made it way too easy for me), I think that underground water, which will have natural ions in it, might affect the fields you could detect on the surface, so, yes.