Vasey's pondweed is a submergent/floating aquatic forb with cylindric spikes, 3-8 mm, with 1-4 whorls of flowers. Its fruits are obovoid, 1.5-2.5mm, with flat or shallowly pitted sides, with or without a low, rounded dorsal keel. Submersed leaves are thin and transparent, narrowly linear, 2-6cm long by 0.2-1mm wide, and sharply acute. Stipular sheaths are free, linear, scarcely encircle the stem, 4-10mm, weakly fibrous in age. Floating leaves are rather sparingly produced on at least some of the plants of a colony, the blades are spatulate to obovate, 8-15mm, 5-9-veined, the petioles are about as long as the blade.