Submerged annuals, occasionally perennating, monoecious. Roots 1-3 per node, simple, densely covered with long roothairs, penetrating substratum spirally. Rhizome creeping, matted, sympodial. Stems simple or sparsely branched, erect. Leaves ternate, opposite or alternate, linear, sessile, with a free cupular sheath subtending axils, or leafbase expanded into a folded sheath forming auriculate stipules above; axillary scales 2, minute. Flowers unisexual, solitary, or with a collateral vegetative bud or one of opposite sex beside it. Male flowers ephemeral, on long filaments (pedicels); anthers 4- or 8-sporangiate, with an apical knob; pollen globose, copious. Female flowers surrounded by a spathe, solitary or pseudo-umbellate; carpels (1-)4 or 5(-9), surrounded by a closely appressed flask-shaped 'perianth'; style exserted, tubular; stigma spoon- or funnel-shaped, large, with wavy membranous margins, ephemeral; ovule pendulous. Fruit a somewhat bean-shaped drupelet, stipitate and crowned with persistent style, pectinate on dorsal and occasionally on ventral side. Seed with a long, spirally coiled hypocotyl. x = 6 (7, 8) (polyploidy).
Species +/- 6 or 1 polymorphic species: Zannichellia palustris L., cosmopolitan, throughout sthn Afr. in brackish pans in arid areas and in estuaries and lagoons.