Lisa: Bill Cody sent your link my direction, and it immediately stumped me. I've never seen such a plant! When (exactly) did you first notice it's presence - and do you have any idea of its origin?
I've submitted a composite photo of your plant (linked below) to a well versed PhD at Texas A&M. Although I'm certain that your plant isn't found in our parts, the fellow at A&M is "well traveled" and may be able to offer an ID. I'll keep you posted if and when I hear back from him.
MA Aquatic Plant 
