I'm not near you, but have some tips which you may have heard already:
1. Keep the coil close to the sand without bumping, all the way through the swing. So, keep it level. The more you pendulum/golf swing it, the less targets you'll hit. Others on the beach do this, which leaves more for you to find.
2. Try to make a grid and be patient.
3. Skin so soft! Apparently the biting beach flies have a thirst for Off and Repel. I'm told Skin So Soft works good. Else, wear long pants and long sleeves. The flies chased me away last week and I had to end my day early.
4. In wet sand, with your machine, lessen the sensitivity and see what you can discriminate out to eliminate false signals.
Good luck, report your finds!