Plants perennial, in fresh water, usually with reddish tinge particularly when dry. Rhizome slender. Stems terete, 1.5–2 mm in diam., simple, but sometimes with horizontal stolons. Leaves dimorphic; stipules axillary, convolute, herbaceous, slightly amplexicaul, 12–35 mm. Submerged leaves sessile, lanceolate to linear-lanceolate or elliptic-oblong, 5–38 × 0.7– 3.3 cm, 9–19-veined, with broad rows of lacunae bordering midvein, base cuneate, margin entire, apex obtuse. Floating leaves petiolate; blade elliptic to broadly lanceolate, 4–9 cm × 8–25 mm, leathery or subleathery, (5–)7–13-veined, base cuneate to narrowly cuneate, margin entire, apex obtuse. Spikes cylindric, 6–15 cm, densely flowered; peduncles thicker than stem. Carpels 4. Fruit obovoid, 2.6–3.7 mm, abaxial keel somewhat sharp, with a short beak. 2n = 52.