Surface leaves of floating pondweed (photo by Maria Gross).
This is a very common pondweed in Conway Lake. Floating leaves are green and 1.5 to 4" long, 1-2 inches wide. Leaves are firm, oval-elliptic to egg shaped and have 17-37 veins flanking the midrib. Leaf edges are toothless and the tip is pointed to rounded.
Submersed leaves are sparse and are generally modified to be long and needle-like or ribbon-like, 3-8 inches long and less than 1/8 inch wide.
Surface and submerged leaves of floating pondweed (Wikimedia Commons).