Originally Posted by
MechEngr
It looks like it is sitting on sand after the tide went out and the sand dried. Then it got flipped over. There is the crescent of black paint that mimics the shadow that was an optical illusion when I first glanced at it.
Per the response to CaleysCoachman , the item was placed onto the beach and then photographed.
But yes, you are 100 percent correct regarding the crescent/arc of black paint at the edge of the item.