Herbs, annual or perennial, aquatic, rooted in mud or free-floating. Stems of 2 types, vegetative and flowering; vegetative stems indeterminate, bearing many leaves, glabrous; flowering stems determinate, usually emersed, bearing single leaf, spathe, and terminal inflorescence. Leaves of 2 types, sessile and petiolate; stipule marcescent, apex truncate, associated with petiolate leaves only; sessile leaves submersed or rarely emersed, forming basal rosette or alternate on elongate stem, blade linear to occasionally oblanceolate, base sheathing, margins entire; petiolate leaves floating or emersed, blade cordate, reniform, or ovate. Inflorescences paniculate, spicate, umbellate, or 1-flowered; spathes bractlike, folded or clasping, commonly with acute to caudate extension. Flowers sessile, 3-merous; perianth with tepals connate proximally, yellow, blue, mauve, or white, tube tubular or funnelform, limb 6-lobed; stamens 3 or 6, adnate to perianth; pistils 3-locular, 1 or 3 developing to maturity; placentation parietal or basal; ovules 1-many. Fruits capsular or utriculate. Seeds smooth or with longitudinal wings.