Potamogeton diversifolius Raf.
Family: Potamogetonaceae
common snail-seed pondweed, water-thread pondweed
Potamogeton diversifolius image
Robert W. Freckmann  
Etymology: Potamogeton: from Greek potamos, "a river," and geiton, "a neighbor," because of the habitat
Plants: perennial, submersed aquatic; stems freely branching; slender rhizomes
Leaves: alternate, entire, linear, 1 prominent midvein, 2 faint side veins; elliptical floating leaves long; submersed - fine, 0.2mm wide
Flowers: green-brown, small; inflorescence spike
Fruits: dry seed with a flat, round, tiny beak, fruit spikes globular from submersed leaf axils; cylindrical from floating leaves
Habitat: water < 7'; in soft sediment soil