Najas minor

About

Najas minor, known as brittle naiad or brittle waternymph, is an annual aquatic plant, a submersed herb. It is native to Europe, Asia and North Africa from the Netherlands to Morocco east to Japan and the Philippines, including China, Siberia, Central Asia, Iran, Turkey, Ukraine, Germany, France Italy and a host of other countries. It is now introduced to North America and considered a weedy invasive species in the eastern half of the United States from Florida to Oklahoma to New Hampshire to Ontario to South Dakota. This plant prefers calm waters, such as ponds, reservoirs, and lakes, and is capable of growing in depths up to 4 meters.

Summary from Wikipedia