My guess is Curly Leaf pondweed - not American pondweed, due to the more slender and curly appearance of the leaves. Also, American pondweed leaves will lay down on the water like a Lilly-pad more than grow up and out of the water like the leaves in your photo.

I prefer American pondweed over Curly leaf as it's less dense - not sure if CLP can become a management issue - but experts can help guide here.

Many men go fishing all of their lives without knowing that it is not fish they are after. ~ Henry David Thoreau

[Linked Image from i1261.photobucket.com]