Undaria pinnatifida is a large brown alga belonging to the order Laminariales, with 3 clearly recognizable parts comprising its visible thallus: blade, stipe and holdfast. The thallus can reach 1 to 3 meters in length. The blade is lanceolate and broad with a prominent midrib, and translucent with color ranging from green to yellowish-brown to dark brown. The blade could also be described as triangular and lobed. Undaria pinnatifida can be found in the upper part of the infralittoral (subtidal) zone, from low tide level down to depths of 10 to 18 meters.

Source: Pereira, L. 2012. MACOI, Portuguese Seaweeds Website. World-wide Electronic Publication. IMAR, Department of Life Sciences, University of Coimbra, http://macoi.ci.uc.pt.