Here, we’re watching a shifting southerly wind fluttering the waters of Great Cove while seaweed fans sway in rhythm.
The fans are “knotted wrack” (Ascophyllum nodosum), our most abundant “rockweed.” They’re fascinating organisms that are ‘knotted” with little air bladders that float their “blades” up to get needed sunlight when the tide comes in.
They’re called “wracks” because “sea wrack” is an old name for “seaweed.” “Wrack,” once meaning something that is cast up from the sea onto the shore, became “wreck”; “ship wrack” became “ship wreck.”
Knotted wrack is neither a weed nor a true plant; it’s one of our marine algae that hosts other lives. It's one of the seaweeds that attach themselves to rocks, hence their common "rockweed" name. They have no roots; they have “holdfasts” that glue them to hard surfaces.
At low tide, their graceful fans look like very bad wigs:
(Brooklin, Maine)