Aquatic perennial; culms 25-130 cm high, spongy, erect or ascending from the creeping lower portion, this usually rooting at the nodes. Leaf-blades linear to narrowly lanceolate, (8-)15-30(-50) cm long, 6-14 mm wide, subcordate at the base, flat, glabrous, blunt or sharply acute; sheaths glabrous and ± loose. Panicle ovate or oblong, 10-30 cm long, the branches naked below, the lowermost whorled. Spikelets narrowly lanceolate, 3.24 mm long, glabrous, acute or shortly acuminate, appressed to the branches; lower glume orbicular, hyaline, up to a quarter the length of the spikelet, obtuse or truncate, nerveless; upper glume 7-nerved; lower lemma 9-nerved, its palea well developed or absent; upper lemma pallid, smooth and shining.