Aquatic caespitose perennial herb from a ± globose woody base, firmly attached to rocks by stiff radiating roots.Leaves fern-like in appearance, few to numerous from rootstock apex, trailing, submerged, up to 55 cm long, narrowly elliptic to lanceolate in outline, pinnate.Petiole 4–20 cm long, covered with ovate, triangular or lanceolate emergences, interspersed with linear or filiform, sometimes branching emergences towards the apex, especially on the lateral margins.Rhachis with numerous ovate to triangular emergences on dorsal and ventral faces, interspersed with lanceolate to linear emergences particularly along lateral margins and towards apex.Pinnae in 55–80 pairs, subopposite to alternate, up to 3.5 cm long, tapering-cylindric to ellipsoid-oblong in outline, bearing branching, filiform emergences all around the pinna axis; filiform emergences 3–5 mm long.Inflorescences scapose, pendulous in bud, stiffly erect at anthesis, few to numerous, spicate.Female inflorescences c. 30–40 cm long; peduncles to 20–30 cm long, covered with emergences; spikes 200–300-flowered; bracts 0.2–0.4 mm long, oblong-elliptic in outline, conchiform with numerous ovate tubercles towards the apex and a flange-like faintly 3-lobed apical appendage.Ovary c. 2 ? 1.5 mm, ellipsoid, with a bundle of hairs on each side; styles c. 4 mm long.Male inflorescences up to c. 30 cm long with a dull pale pink axis; peduncles up to c. 20 cm long, densely covered with emergences; bracts 1.5–2.5 ? 1.5–2.5 mm, with numerous tubercles towards the apex and a rounded to faintly 3-lobed apical lip, decurrent at the base, pinkish with a dark purple apex.Anther thecae 0.75–1 mm long, elliptic.Fruit not seen.