I was fascinated to find dozens of these Onchidella borealis or Leather Limpets on a huge rock during a minus tide. Some were crawling among barnacles and others were crawling on Katy Chitons. The rock is normally submerged. I had never seen these tiny critters before, all less than 1/2" long, and with pretty beige points all around their bodies. The antennae/eyes (?) have a little black dot, giving this animal a cute appearance. Wikipedia says this is an air-breathing sea slug, and at first I thought it was a tiny nudibranch.