I wanted to see how the F75 would handle the iron rich sand of my local southern CA beach this morning. I initially tried to GB using fastgrab in discrim mode, which told me the GB level was about 85. The machine was still too chattery, so I disregarded that reading. Time to manually GB in all-metal mode. I was able to reduce the coil pump noise the most by manually GB'ing to a level of about 5 (yes five). Oh, I found that I needed to back the sensitivity all the way down to 50 as well. I usually run it at 70 on land. This allowed me to hunt in all-metal mode with a nice threshold hum, though there was a little bit of falsing at the end of each sweep. Targets came through clearly and I found a silver (marked .925) ring at 4 or 5 inches, which gave a digital readout of 55-60, even when I put the ring on the surface of the sand. Clad quarter from 5 inches or so gave a consistent 82-83. Steel and iron targets (nails, hairclips, bobby pins) came through loud and clear, but the odd thing was that they did not register a digital readout at all. I concluded that the machine can handle wet salt sand, but you will want to use it in all-metal mode and really fiddle with the GB to quiet things down. Hope this helps anyone out there who is considering using the F75 at the beach.
Jim
Jim