The thallus of Dictyota dichotoma grows in tufts and is a yellowish-brown or greenish colour, with a faint bluish iridescence when underwater.

The tufts are semi-erect and have little or no stalk; they are anchored to the seabed by rhizoids, filamentous outgrowths that can absorb nutrients from their surroundings.

Clusters of spores develop in round or oval sori under the surface of the thallus, finally bursting through.

The sporophytes and the gametophytes are similar in morphology, and the reproductive organs appear on the thallus as small, dark-coloured spots.

[4] Also present were a range of other chemical compounds including alkaloids, steroids, tannins, flavonoids, phenols, coumarins, quinones and glycosides.