Well I know this pick is bad-try and get some better ones. This stuff has infested our spillway and seems to grow just aswell on the banks out of the water like a creeping vine. I have hit around the edges with reward and killed it fast. When I rake the dead plants from the surface there is healthy green plants under it! Any ideas! My extension service thinks it's some type of milfoil and suggested the reward. What is the best way to remove the dead material and am I spreading this stuff by raking it out. I didnt know milfoil could grow so good out of water.

Since it's growing out of the water I'm thinking it's parrotfeather (hard to tell from the photo). Try to get a pic of it at your spillway.