submersed plant with whorled lanceolate leaves and solitary axillary flowers; Old World plant naturalized in southern United States and clogging Florida's waterways

submerged aquatic vegetation (SAV), Hydrilla verticillata; non-native invasive plant with branched stems up to 25 feet long; found in all types of water bodies.

Hydrilla is an aquatic plant, native to cool to warm waters of Asia, Europe, Africa and Australia.