Not enough exposure range?  Should use a UV filter for the sky?  Perhaps a little Polarizer?  Perhaps spend more than 10 seconds taking the shot?

I need a super wide, (the 24 mm is actually a 30mm perspective in 35mm), or spend more time.  (I'll admit I have to work on my photo technique when I'm covered in neoprene.)

The crab shell has the same mottling that the beach sand has - I'm sure in a monocromatic vision
system, it's harder to see.