Sand fleas.
Giant kelp bulbs litter the beach, almost entirely all devoid of their leaves.
I stepped close to this one and the sand erupted with hordes of tiny sand fleas. I started looking more closely and found more bulbs with their leaves in various states from pristine to completely consumed by sand fleas.
I flipped a few leaves and could whitness hundreds of these critters boiling out of the wet sand. Something entirely new to me. And I've spent a good part of my life hanging around the ocean in this county.