Aquatic, glabrous herb with thick stolons bearing tubers at tip. Leaves mostly emerged, upright, sagittate or somewhat hastate, blade ovate or linear-lanceolate, (5-6.5-) 8-17 cm long along midrib, (1.5-2.5-) 5-7 cm broad, acute, basal lobes triangular or linear-lanceolate, often longer than the blade, sharply acute; petiole 60-75 cm long, triangular. Inflorescence an unbranched scapose raceme, 30-50 cm long. Flowers in 2-6 whorls of (2-) 3 (-5) flowers each, unisexual, 1-2 cm across, white; pedicels 8-15 mm long, short in females; bracts triangular-ovate, 8-10 mm long, 3-4 mm broad, acute-acuminate. Sepals elliptic, 6-8 mm long, 5-6 mm broad, somewhat keeled, margins broadly membranous, reflexed in fruit. Petals broadly elliptic-suborbicular, 12-15 mm long 12-15 mm broad, white, without basal purple spot. Stamens c. 20, filaments lanceolate, 1.5-2 mm long; anthers yellow, oblong, as long as the filaments. Head of achenes subglobose, c. 1 cm across; achenes triangularly obovate, with laterally bent beak. c. 2-3 mm long, wings subcrenate to entire.