Rhizomatous. Stems to more than 1 m. Leaves all submerged, translucent, mostly yellowish-green, subsessile to petiolate; petiole to 2 cm, lamina oblong-lanceolate to obovate-elliptic, 5-15 cm, acute to cuspidate at apex, cuneate at base, margin often undulate, ± serrulate; occasionally leaves reduced to phyllodes. Stipules to 7 cm, herbaceous. Peduncles to 20 cm, thickened upwards; spikes to 6 cm. Fruitlets 2,5-3,5 mm, obovoid to roundish. Fl. 4-7. Lakes, pools, channels, s.l.-2300 m.
Most of Europe, Mediterranean area, Caucasus, N. Iraq, Syrian Desert, W. Iran, Siberia.