This green algae have a stalk with sheet-like aspect, stiff at the base and more delicate in the region of the ends. It has a large variety of sizes and growth forms and often have small perforations. This alga is able to withstand large variations in salinity. Can be found in clusters of several sheets or singly, mostly.

Source:https://seaweedindustry.com/seaweed/type/ulvarigida and http://www.seaweed.ie/descriptions/ulva_rigida.php