Plants light green, less than 30 cm long and soft, 20-80 mm tall, thallus repeatedly branched in all directions, cylindrical or compressed with narrow branchlets as much as 40 cm long, with a hollow medulla and a single cup shaped chloroplast and cells more or less quadrangular in shape. Plants grow first attached to the substratum but later become free floating. In nature many form a dense mat, almost resembling a lawn or a bed of moss. Ulva clathrata can be found from the intertidal through the subtidal zones of coastlines, often found on reef crests.