The United States Geological Survey has an interesting FAQ report on dowsing — the practice of attempting to locate underground water with divining rods. It’s got some interesting history and comparisons between dowsing and modern hydrology. The part on evidence for and against dowsing, though, is pretty sparse. If you want more on that, The Skeptic’s Dictionary has some deeper analysis. The basic gist — what little research there has been suggests the successes of dowsing aren’t any better than chance. (Via an interesting piece by Mary Brock at Skepchick about dowsing in the wine industry.)