Dasya sessilis is a red alga native to the Northwest Pacific from the Philippines to Russia. It has been introduced to the Netherlands, Spain, Portugal, and Mediterranean France, and southern California. This plant has an alternating life cycle with asexual tetrasporophytic plants and sexual gametophytic plants . The plants are attached to a holdfast have several erect stems 50-250 mm tall in tetraspotophytic plants, and 60-130 mm in gametophytic plants The plants have many branes, leading to finer branches, covered by hair-like branchlets. The color of the plant ranges from rose-red to shocking pink. It was first collected in 1976 in Long Beach Harbor, and has been found in San Diego, and Huntington Beach. The seaweeds were attached to concrete pilings and floating docks. In southern California, the likely vectors were ballast water and hull fouling. In Europe, culture of Pacific Oysters is a more likely vector.