An HDR with a bit of post processing
No tips on the post processing for you. It looks great.
However some tips on taking the photo. It seems a little soft. I think there are 2 reasons for this:
1) Your focus plane is too close. Since there is no specific object, just the sand in the foreground, you should have focused about 10ft out from the camera. Once you get down to 5ft or below distance objects will start to blur.
2) Too small an aperture. f/20 is really unnecessary and cause some serious diffraction. f/11 is a popular max f-stop because lenses still tend to be sharp at that aperture and if your focus plane is 10ft out from your APS-C camera, your in-focus range is still from 5ft to infinity. Perfect for landscape.
Play with a depth of field calculator to see what I mean.