Art,
That's a great story, and it's from what I think most people here *might* agree is a credible source: Stanford University's Journal of Scientific Exploration.
Admittedly this is just one study, but it does give a provisional answer to Beeper's question about the success ratio of dowsing for water vs using "conventional" hydrogeological methods, with dowsing performing much more consistently.
A long time ago, I did call several well-drilling companies in my area and asked them if they dowsed. I think 2 of the 4 who spoke to me said they did employ that method.
Personally I don't see why people find dowsing for water so unlikely: I don't know about a "treasure sniffing dog", but animals can smell water, can't they? You know how you can "smell rain" sometimes - I don't know the science myself, but I'm told it's because of negative ions.
Anyway, that people could locate water seems entirely within the realm of the possible to my mind. Now dowsing for other things --- that remains open to question, but I'd like to remain open-minded and I look forward to checking it out for myself. If I succeed, so much the better, and if I do not, I will have fun anyway!
Best,
S.