I am saying a species of pondweed, my best guess is either baby pondweed or bushy pondweed. Sago pondweed has a little finer leaflets but there is variation among the same species. I am surprised your grass carp aren't feeding on it more. From the picture you show in the water, it doesn't look like it is very abundant. Mostly just along the edge. I like aquatic vegetation like that. It gives young GSH and other forage fish a bit of a refuge. Great photos though, Bill Cody is way more knowledgeable on pond plants than I am. If he sees this post perhaps he can give you a firm ID.
