FP, Bill gave a very good answer for a hard question. Things like water clarity, average pond depth, fluctuating water levels, all come into play. After John's previous posts, I added curly leaf eel grass to a small pond I have, and have very happy with the initial results. But, I can control the water level as needed, and I'm not sure how this would work if you have big water fluctuations.
I would probably get with the state fisheries dept and see what if any plants they are adding to public waters. Also, there may be venders that sell plants in your area. They should know the best plants for your plans. Right now, bog plants look very appealing to me.
Here's a link to a vender that sells plants here in TX. I have no personal experience with him, but it is informational.
LINK As Bill said, be very careful. Plants can spread quickly and become an issue.
