Perennial herbs. Leaves with basal sheath open, free and ± encircling the branch, auricles absent; sheaths often decayed and inconspicuous on older parts; lamina linear to orbicular; apex entire. Inflorescence a few- to many-flowered spike, emergent. Anthers 4; pollen ± spherical. Carpels 3–5; sessile. Infructescence as for inflorescence (cf. Ruppia). Fruit with inner hard tissue remaining.
About 100 species; 11 species native to Australia and 1 or 2 naturalized, 7 species native to Victoria.
Pollination is thought to occur above or on the surface of water either by wind, insects or by floating across the water.