While these organized structures might look like the work of an artist, they’re actually just the remnants left behind where a sand bubbler crab’s been snacking.
During low tide they exit their burrows (as seen in the top pic) to scour the sand for tiny bits of organic debris in a radial motion. While eating, the crabs ball the excess sand on their heads, then discard it when it gets too big for them to see over, leaving behind a remarkable-looking reminder which helps them keep searching for food in the same sand twice. Each time the tide returns, the small structures crumble and are washed away, all the while leaving behind more food particles for the next time.
And a video of the crab in action: