Rhizomatous aquatic. Leaves floating, lanceolate to linear. Flowers distichous, white to lilac, with 1-3 tepals, stamens usually 6.
Tubers globose, up to 3 cm in diam., greyish brown. Leaves heterophyllous; filiform to subtrigonous, 4-25 cm long; or apically expanded into an erect spathulate lamina; or a floating, oblong blade up to 17 cm long and 4-5 cm broad is formed, with the base and apex attenuate or rounded. Spikes bifid, usually 2-4 cm long and 8 mm broad (up to 9 cm long and 2.5 cm broad), lengthening during anthesis, many-flowered. Flowers bisexual or female,(through suppression of stamens), scentless, situated dorsally on the rhachis or only so near the base, with the upper flowers arranged all around the rhachis; perianth-segments 1.2 or 3, oblong-lanceolate, white, pink or mauve, with a shiny, soft texture, becoming green and firm with age. Stamens usually 6, slightly longer than the perianth-segments, equalling more or less the carpels; filaments swollen at the base, tapered above; pollen ellipsoid. Carpels up to 18 cm lower flowers, usually 76 mm upper, ovoid, with a curved beak above, stigmatic ridge dark, ovules 1-8, basal. Follicles green, firm, somewhat transparent, 3-5 mm long; seeds fusiform, 2 mm long, outer spongy covering thin; usually 1 or 2 seeds ripening per follicle.
Fresh-water aquatic with tuberous rhizome. Tuber globular or obovoid. Leaves 40-430 mm long, needle-like or band-shaped, usually without a blade, often upright and emergent. Flowers: inflorescence with 2 spikes, flowers arranged along one side; perianth segments with 1-7 veins, ± 4 mm long, white or pink; Oct.-Apr. Seeds with 1 coat.
Common in fresh-water ponds, marshes and rivers, growing on the bank, or submerged with the lamina floating and the flower spikes exserted.