Hydrilla-Click for more info

Non-Native and rapidly spreading across the US.

Hydrilla is a submersed plant. It can grow to the surface and form dense mats. It may be found in all types of water bodies.
Hydrilla stems are slender, branched and up to 25 feet long. Hydrilla's small leaves are strap-like and pointed. They grow in whorls of four to eight around the stem. The leaf margins are distinctly saw-toothed. Hydrilla often has one or more sharp teeth along the length of the leaf mid-rib. Hydrilla produces tiny white flowers on long stalks. It also produces 1/4 inch turions at the leaf axils and potato-like tubers attached to the roots in the mud.
University of Florida, Center for Aquatic and Invasive Plants