Did you get this figured out? I can not tell if it is growing in the water, on dry land, or both. A close-up of a plant (maybe laying on a white background) and any flowers that might be on it would help. Knowing if it is a emergent (growing from the water), marginal/bog (can grow at the waters edge in very shallow water or in the adjacent muds), or if it is a terrestrial plant (grows from dryer soils) would also narrow down the search.

Fish on!,
Noel