Usually robust, sometimes slender, perennial, aquatic herb. Rhizome woody, fibre-covered, 7–18 (–30) mm thick. Tubers usually elongated, 20–145 mm long, 4.5–13 mm diam.; terminating long roots c. 3.5–20 cm long. Leaves ± flat and strap-like, floating to erect, glossy above, to 350 cm long and 5–41 (–150 in western variant) mm wide, spongy basally; basal sheath tapered; T.S. c. 3 cm below sheath summit ± elliptic, with width of spongy portion c. 2.2–5.5 times its thickness and with sheath margins not or just meeting across blade face (but see note below on an eastern variant). Scape at fruiting c. 27–145 cm long, 4–23 mm diam. Infructescence a raceme, 6–51 (–144 in western variant) cm long, 17–29 (–42 in western variant) mm diam.; pedicels 2–5 mm long. Fruits c. 52–320 per infructescence, ± globular to broadly obovoid to ellipsoid, 6.8–14.4 mm long, 6.8–10.9 mm diam. Carpels 3–6 (–7), all maturing or 1 or 2 (–5) aborting; central axis absent; mature carpels attached along 45%–80% of length, straight to twisted around each other, with a broad-convex dorsal ridge and usually 2 broad lateral ridges, lacking projections except short stylar beak.
Common in still to slow-flowing fresh water to 2 m deep mostly in permanent swamps, lagoons and streams, but withstands stranding for extensive periods. Abundant in Eucalyptus camaldulensis sites. Sometimes in brackish water (eastern variant).
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