I never did, but read an article on it once (maybe 3 years ago). It seems that in some areas it can be quite lucrative - so much so, that people have been shot for "golf ball poaching". From what I remember of the article, most divers get contracts with the golf course(s) to dive the ponds. And it's pretty much braille diving, just feeling your way across the bottom of a mudhole... is that a ball? or a snake? or an aligator?...