Hey BB:
There is a little known technique that a few TH'ers use. Can't guarantee that it will work but it'll get you down where you "might" find something.

At low tide, on the wet sand, start digging a trench, a couple of feet wide and a couple of feet deep. Pile the sand up between the trench and the surf. As the tide returns later in the day, it'll slow it down some. If you time it right, you might have the trench for a few hours. Search the sand piles and inside the trench from all angles. If you have a GPS, make a notation of the beginning and end of the trench. That way you don't cover the same ground twice. Its slow and back breaking but you gain two feet of depth which is deeper than many metal detectors can go. It might improve your odds. You won't have to refill the hole in as the returning tide will do that for you. That is why, GPS is crucial along with a notebook for entries.