I took my minelab Excalibur 1000 to the beach and it would not work on the wet sand. All you could hear is the threshold and when the coil touched the wet sand, it would go silent as if there was iron. I placed a quarter at 4 in and it wouldn't pick it up. I adjusted the sensitivity many times too. Then I took it to a park and it worked just fine. What do you thing is wrong with it?