Schoolofhardnox,, had the same exact stuff going on with mine, at one certain huge beach area, regardless of literally every setting/mode/sens/gb attempted, just endless iron sounds and couldn't hit anything deeper than like 4-5 inches. Freshwater, Lake Mi. Then, at other beaches I went to, did just fine and very deep. The problem beach had multi layers of magnetic sand all throughout, but never had any issues in the past there, with hundreds and hundreds of hours with nox & then legend. Due to an injury, haven't been able to go back and experiment yet, will be several weeks.