Rhizome absent or filiform, compressed to almost terete, annual, short. Stem sparingly to richly branched, filiform to slender, strongly compressed to flattened, 0.4-3.0 mm wide, annual; axillary or apical dormant turions developing. Submerged leaves sessile, linear, 35-80(-135) mm long, 1.8-3.8(-5.5) mm wide, 13-30(-40) times as long as wide, bright green to dark green, sometimes with a reddish tinge, 3-veined, with 16-24 additional sclerenchymatous strands, bordered by a strong marginal vein, with narrow rows of lacunae bordering the midrib, entire at margins, narrowly cuneate at base, acute to acuminate at apex. Floating leaves always absent. Stipules axillary, convolute, 10-21(-29) mm long, translucent to opaque, persistent but soon eroding to fibrous strands at the apex. Peduncles 3-15(-26) mm long, 1-6 times as long as the fruiting spike, as thick as the stem. Spikes almost globose, 4-8 mm long in fruit, contiguous. Flowers 4-7, with 1 carpel. Fruits 3.0-4.0(-4.7) mm long, dorsal keel distinct.