Herbs, annual or facultatively perennial, rooting in mud. Vegetative stems submersed with elongate internodes, or emersed and short. Flowering stems submersed and extending to water surface, or emersed. Sessile leaves forming basal rosette. Petiolate leaves floating or emersed; blade cordate to hastate, apex acute to acuminate. Inflorescences umbellate or paniculate, up to 30-flowered, elongating in 1-several days; spathes folded, sometimes with ovate to caudate extension. Flowers: open 1 day only; perianth with tepals connate basally, blue or white, limb lobes distinct, narrowly ovate to lanceolate, glabrous, apex acute; stamens 6, 1 with anther 2 times larger than others; filaments winged, glabrous; anthers yellow or blue, ovoid; ovary incompletely 3-locular; ovules many; style 1. Fruits capsular, ovoid. Seeds 10-200, ovoid, testa with longitudinal wings.