Semi-aquatic small perennial herb, often stoloniferous. Leaves erect to ascending, usually 1–6 cm long, lamina not differentiated, or oblanceolate and up to 12 mm long and 1–3 mm wide, apex attenuate, base tapered. Pedicels slender, erect in flower, sometimes recurved, usually 8–25 mm long in fruit. Calyx 1.5–2 mm long, red-purple below sinuses between the teeth; corolla c. 2 mm long, white, lobes often purple externally; anthers black, with white pollen. Capsule broad-ellipsoid, 2.2–2.8 mm long, 1.8–2 mm diam., dark brown, sometimes recurved into mud, with curved caducous style 0.8–1.2 mm long. Flowers mostly Aug.–Apr. (when exposed or sometimes when lower parts inundated).