Cork screw is not all that invasive compared to milfoil, Elodea, some small leaf potamogeton, etc. I've never seen corkscrew at 3 ft tall. There are a couple varieties of corkscrew / sprial eel grass. I suppose some are taller, some shorter at mature height. If you want a shorter plant than corkscrew try dwarf sagittaria (Sagittaria subulata).
