Three types of vegetation are described from the Bitter Lakes, within the Suez Canal water system: (1) The vegetation of the sandy flats (which comprise most of the Lakes' bottom) is poor in species and is dominated by Halophila stipulacea. (2) The vegetation of rocks and other hard substrates is rich and includes several plant communities, both intertidal and infralittoral. (3) A very special type of vegetation is the rock-forming community of blue-green algae, responsible for the formation of the recently and currently formed beachrocks found on the coasts of the Bitter Lakes. The nature of the vegetation of the Bitter Lakes, the constancy of plant communities in the Suez Canal, and the environmental conditions required for beachrock formation in it, are discussed. It is indicated that the vegetation of the Bitter Lakes has some characteristics in common with lagoons situated on other coasts of the Sinai Peninsula. Main plant communities which occur within the Canal system at present seem to be the, same as those observed by the Cambridge Expedition to the Suez Canal in 1924, thus they seem to have stayed unchanged for at least the last five decades. It is also indicated that the type of beachrock formation which takes place at the Bitter Lakes at present requires shelter from intensive wave action.