Rhizomatous. Stems to more than 1 m, compressed. Leaves submerged, green to brown, linear to narrowly oblong, 35-70 x 5-12 mm, sessile, 3-veined, obtuse to acute at apex, obtuse to rounded at base, undulate, margin serrulate . Stipules usually c. 5 mm, membranous, open, evanescent. Peduncles to 5 cm. Spikes to 1.5 cm, lax and fairly few-flowered. Fruitlets 4-5 mm, rostrate, beak equalling or longer than body of carpel Fl. 4-8. Lakes, channels, rivers, s.l.-1950 m.
Temperate Eurasia, Africa, Australia, N. America.