Alas, the angle won't work
Yep, that's what I was thinking too. And it's easy enough. Just sample the sand colour with your eyedropper tool, then add a Solid Color layer of that colour, and set it to "Color" blend mode; then mask on carefully.
Well, I'm not sure, exactly. I suspect your noise "Detail" and "Contrast" sliders (which you have both presently set at 84) are too high as well. But until I see it without the awful sharpening, I can't really tell.