A large sturdy brown alga 0.3 -1 m in length (occasionally up to 2 m) rising from a strong, flattened cone shaped holdfast. The main stem is flattened and branches alternately to give a distinctly zigzag appearance. The stem bears a few, flattened ribbon-like 'leafy' fronds. The ends of some branches bear characteristic pod-shaped air bladders (about 0.5 cm wide by 1-4 cm long) that are divided by transverse septa into 10 or 12 compartments. The branches also bear reproductive bodies that appear similar to the bladders but lack the septa. Young plants are olive-green in colour while older specimens are dark brown and leathery. This species is perennial.