I believe these are Shanny (Lipophrys pholis), also called Blenny. As the tide pulled out it left these crystal clear pools of water and in them they teemed with these young fish which moved nimbly through the shallow water. They are so well adapted to their environment you would hardly notice them until they moved.
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Shanklin Beach, Isle of White, England, August 2018 © Pete Hillman.
Nature Journeys 