Some machines get even deeper in the sand than they do on land, and it's hard to judge coin depth in sand as it can easily move and fall further down the hole. On land for me just this past year I dug a v nickle in one hole and an indian in another at 11". That was under ideal wet conditions which I'm sure helped. They both gave perfect and strong coin IDs so I suspect they could have been even deeper and I still would have got them. Up until my current machine all the ones I've owned in the past could only muster about 7.5 to maybe 8" max in my moderate to heavy mineralized sites, so I was very shocked to start popping silver dimes and wheats at 8 or 9" deep, let alone the 11" ones.
Alot of what you hear about depth reports on the web has to do with their mineralization. If they have real neutral good black soil then they'll get coins a good bit deeper than you on a more regular bases. The exact same machine used in another part of the country could get close to half the depth others are able to achieve with it in their soil. Even the best machines on the market in terms of being known to handle ground minerals well suffer from this problem, although not as bad as some other machines do.
