jjg,
I don't know about the beach (am a land hunter hundreds of miles from the nearest sea/ocean/gulf beach) as mostly I hunt dry land. However I have wondered if mounting a "super magnet" on a stick, or perhaps on the handtool digger I use, might help in pulling out scrap iron (nails, bolts, screws etc) whilst detecting. I have several of the super magnets, and know the meteorite metal detector boys use them for meteorites with great success.
Can't see why they would not fit in the tool kit of regular metal detector/coin shooters also.