What Is Bletonism?

Bletonism is the art of finding water underground by sensation. It gets its name from a Frenchman (called Bleton) who practised this art.

Bletonists are also called water dowsers or diviners. They often use a forked branch of a tree, bent pieces of metal or plastic wire or a small pendulum to indicate when water is present.

There is no scientific evidence that bletonism works or any accepted scientific reason why it should. It's pretty impressive when you see it "working" though. Mumbo-jumbo-meter: 7/10.
A list of divination techniques