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.
Caulerpa sertularioides
The seaweed has a pale to dark-green thallus that typically grows to outward to around . It has feather-like fronds that arise from a common stolon. Each of the fronds is upright and branched. The opositely arranged branchlets are cylindrical to needle-shaped with upcurved tips with a blunt point at the end. Each branchlet has a length of and is attached to a cylindrical axis in the middle with a diameter of . Each axis connects each frond to a creeping stolon with a diameter of and a length of up to . Stolons are branched out to slim points and rhizoids then form from bottom surface these fork and penetrate the sandy substrate firmly anchoring the seaweed to the seafloor.