after i saved the photo and rotated it! it looks like you got a crab on your head!
i believe Butt-Head would say "Hey Bevis, that guys got crabs heh heh heh! yeah Butt-Head he's got crabs yeah yeah crabs crabs humpf humpf. lol
It is the light entering your pocket on the other side.
You can tell that it fits the picture because your arm is so high up when reaching in it. Especially at the angle your wrist is. It is nothing more
than the light reflecting off the inside of your pocket. If you do some light matching with the sand on the ground you'll notice that they are about
that same brightness. Also consider that your hoodie pocket isn't any other shape when reaching inside. So it makes that crescent moon shape when you
open it like so.
That's so weird everyone saw the pic rotated I uploaded it apologized for it being sideways, and then edited that out when on all devices it appears
normal and horizontal. Anyways yea two optical illusions in one picture that horseshoe crab did not look like a mask on the back of my head by any
stretch of the imagination, it hung down my back.