Submerged herbs. Rhizomes creeping, usually slender, branched, rooting at nodes. Stems elongated, slender, much branched. Leaves submerged, sessile, subopposite, or rounded at nodes, linear, margin entire. Flowers axillary, unisexual, monoecious, solitary or in cymes. Male flower solitary, pedunculate, without perianth; stamens 1(or 2); filament slender; anthers 2- thecous. Female flowers with a cupular perianth, sessile; carpels 2–9, free; ovule 1, pendulous; styles simple, slender, elongated; stigmas usually obliquely peltate. Fruitlet achene- or nut-like.

Six species, cosmopolitan; one species in Nepal. (Zannichellia palustris L.)