Aquatic or semi-aquatic rhizomatous perennial; culms 60-150 cm high, rooting and branching from the lower nodes. Leaf-blades tough, linear with filiform tips, 25-55 cm long, up to 5 mm wide, inrolled or rarely flat, scabrid, grey-green with a broad white central nerve. Inflorescence 20-35 cm long; racemes 10-30, slender, 7-15 cm long, more or less straight. Spikelets 6-11-flowered; narrowly elliptic to elliptic, 8-15 mm long, slightly overlapping, grey-green or olive-green; glumes keeled, scabrid on the keels, the lower lanceolate to narrowly lanceolate, 2.1-4.6 mm long, acute or acuminate, the upper narrowly oblong, 3.3-7.4 mm long, acute or obtuse and minutely mucronate; lemmas narrowly oblong, 3.2-5.9 mm long, pilose on the lower part of the nerves, 2- or more toothed and mucronate or shortly awned from the sinus (the awn 0.3-1.6 mm long). Caryopsis dorso-ventrally flattened.