Knotted Wrack (Ascophyllum nodosum) grows on rocks in the intertidal zone, frequently in close company with Bladder Wrack (Fucus vesiculosus) and other Wracks (Fucus spp.). These bladder bearing species are often lumped together as Rockweeds. The strap-like stems of Knotted Wrack are typically dotted with egg-shaped air bladders, a feature that allows the stems to sway to and fro when submerged. Stems can host a red algae called Wrack Fringe Tubeweed (Vertebrata lanosa). Large clumps of Knotted Wrack, that to me resemble mops or thick hair, seem like choice resting spots for sea ducks. (To view the following images in full-size, click here.)
Photographed at Fortune's Rocks Beach in Biddeford, ME.