The sentences in the template should be capitalized.
"it's ancestor" and "it's originating" are typoes.
"swathes" is the British spelling. This isn't a problem, since I can't find any British and American variant conflicts in the description. It would be useful to remember to keep variants consistent in future submissions, though.
"beaches forming" should be "beaches, forming".
"together the surfaces" Do you mean "together on the surfaces"?
"in order to survive" suggests intention, which is discouraged when describing biological traits. "which helps them survive low tides" is better.
"free floating" should be "free-floating". Otherwise, it's less precise: it could be a free (cost-less) floating ball.
"the base following much" is hard to parse.
"pair very large" should be "pair of very large".
"free float and" should be "free-float" or simply "float".
The second paragraph's sentences should be merged together. They aren't long enough or distinctive enough to warrant separation. I also recommend merging the first three sentences and the fourth sentences together to make one paragraph, instead of the first three sentences standing slightly separately from the other sentence.