Canadian waterweed (Elodea canadensis)
Submersed aquatic plant with small leaves in whorls of three. Bushy, dark green appearance near the top. Lower leaves may be sparse along the stem. White flowers born on thread-like stems. Commonly found in soft substrates of lakes, ponds, and streams. Provides refuge habitat for small fish and amphibians. Helps oxygenate water. Excellent aquarium plant.