Plant with elongated, planar, green leaves which measure up to 1,5 m. The flowers come out in the autumn but not every year. The fruits are dark balls, which one often finds washed up on beaches after storms. The same happens with the leaves which wilt and separate from the plant at the end of summer. It grows on sandy substrates, and has a rhizome from which several plants grow. The compact form of its growths retains the sediments pulled by the currents along the sea bed. Neptunegrass forms extensive prairies, always on the continental shelf. The plant's presence, apart from constituting an excellent refuge and food reserve for many species, gives an indication of the maturity and good condition of the whole marine ecosystem.