Stoloniferous, perennial herb, free-floating. Rhizome absent or very reduced. Leaves in a basal rosette; petiole spongy, often inflated and buoyant. Primary bracts 2, subtending the inflorescence. Inflorescence terminal, racemose, appearing spike-like, erect, few- to many-flowered, with flowers usually crowded. Perianth lobes 3–4 cm long; ovary 3-locular with axile placentation. Infructescence recurved and submerged. Capsule 3-chambered; seeds numerous.
About 7 species, in the American tropics, with one species in Africa and Madagascar; 1 species naturalised in Australia.