pondweed: any of several submerged or floating freshwater perennial aquatic weeds belonging to the family Potamogetonaceae
aquatic plant: a plant that grows partly or wholly in water whether rooted in the mud, as a lotus, or floating without anchorage, as the water hyacinth
seed shrimp: tiny marine and freshwater crustaceans with a shrimp-like body enclosed in a bivalve shell