I haven't posted in quite a while... but yes I used to have one.
I bought it kinda as a gimick, and to dive with and play with in the surf when my kids were younger. I dove with it a few times and didn't really find anything. It worked ok... but I had a few complaints and put it back up on ebay (where i got it in the first place). 1. the depth wasn't all that great (5 inches on a good target), 2. the angle you had to cock your arm at to get a decent sweep was uncomfortable to say the least, 3. The footprint was so small, (only about 3" in diameter) that it was pretty ineffective.
I actually used it more as a pinpointer. When I'd dig a hole in the sand, i'd just stick my hand into the hole and twist...
for the money, i wouldn't buy another... but if a great deal came along... i might