You can use any detector on the beach if you stay up in the dry sand. If you wish to detect in the salt water wet sand or in the salt water you will be better off with a multi frequency or a pulse induction detector.
I just got off the phone with White's and they said that MD is now discontinued and it is designed only for raw gold and not a refined gold like a wedding band and it would not work as well in the sand like I wanted to use it for along with my PI MD.