Perception and footprints

Normal perception will show something odd about these footprints (they appear to project upward eg they are raised above the sand). There is no manipulation here, this is as-shot.

Footprints at the beach
Nikon D3s + Zeiss ZF 35/2 Distagon @ f/8

Winter in California, Leap for Joy
Nikon D3s + Zeiss ZF 35/2 Distagon @ f/8