Used it in a state park fresh water swimming area today for the first time. After Labor Day detectors can be used in the water. I got there a day too late, any rings were already gotten by others. Anyway I picked up some tiny pieces they missed, seen in the photo, and they all gave a stong mid tone signal. Thought each one was a ring . I could hardly beleive my 10" coil could find things this tiny. The bottom is sand that was trucked in with clay below. In the past I've only used it at the shore in the wet salt sand, and it goes deep there. The CZ20 is one sensitive detector.