When I went to Florida with my Excalibur, I was getting depth that I would have never believed in the sand. I think the sand for the most part has very little mineralization.
Still, when I was there the wind had been blowing inland and most of the targets were "sanded" in.
It is true that targets will sink fast in sand. But in my experience here in East Tennessee sand has meant more often than not that good finds were there.
Back to the Florida experience, even the slightest whisper in the sand would result in a find. Some of the holes I dug were 18-24" and it would end up being a ligit target. Some of them were quarters. Around here, 8-10" on a quarter would be impressive.
You may have to evaluate your settings and methods of hunting when you hit the sand you are talking about. Possibly, you will find things there that others were also baffled by.
Others may have different examples though.
HH Alton