Seaweed
"Seaweed" is a colloquial term and lacks a formal definition. A seaweed may belong to one of several groups of multicellular algae: the red algae, green algae, and brown algae. As these three groups do not have a common multicellular ancestor, the seaweed are in a polyphyletic group. In addition, some tuft-forming bluegreen algae (Cyanobacteria) are sometimes considered to be seaweed.
Desmarestia herbacea
Desmarestia herbacea is a species of brown algae found worldwide. Its common names include color changer, Desmarest's flattened weed, and sea sorrel, though the last name can also refer to other species of "Desmarestia".