I think it is hydrilla. My town has a lake of about 100 acres, devoid of all trees, that was cleared out when it was built in about 1960. I think this has been a problem before because I recall grass eating carp being put in there. I am not sure that they reproduce? I haven't seen any in a long time, they probably just died of old age. They sure got big and I recall that they did a good job on the grass. Does anyone know how to get rid of this stuff? Will a drawdown do it? Will it die with freezes or do you have to rake and burn it? That's a problem if so cuz the town has no money. Must you use herbicide? This stuff is covering probably half the lake now. The lake is 18 ft deep at its deepest near the dam. This grass is pretty much anywhere from zero to 10 feet or so now. The lake is used for swimming, skiing and gets quite a lot of fishing. For bass, bream and crappie. One thing I am going to say to the town when I alert "town hall" is... imagine you are a skier and you and nobody in your boat is aware of the hydrilla and a young kid falls while skiing or tubing and ends up with that stuff all around his/her legs and panics. That can't be good. If nothing else, it's just scary to many kids.

BTW, fishing in the lake now is pretty much curtailed.

I'll also mention that reeds have completely covered the entire shoreline in this lake and most any lake around here. It didn't use to be that way when I was young. I am not sure if all of them are cattails but that is what it looks like.