For more information on the habitat, vegetation, and weather of the area where I made this observation, please see the journal entry for April 28, 2012 here on iNaturalist. This seaweed was common all over the beach. It looks strange when it's flattened out at low tide. This particular specimen was about 7 inches long and was a light brown color. I thought it was sea lettuce at first, but, as was helpfully pointed out to me, this Porphyra doesn't grow in clumps as with this specimen and sea lettuce does.
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