These were on my deck today after a rain. Each bug/insect is about 1 mm in length. Using every magnifying lens available in the house, they appear to be flea like, with two antennas and 6 legs.They seem to like to huddle, but others move swim-like through the water, and others spring to new locations. Those are 6" wide decking boards.
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is only one section of the deck, they were on other sections, but those pics didn't come out as well.