2016-8-23 - unknown grass - Russell Peterson Wildlife Refuge, Wilmington, DE

Have been fascinated by this plant and unable to find a lead.
I feel certain there are enough clues in the picture to ID it - if not to species, then at least genus. But . . .
Update: today, 2017-10-11, I'm thinking it may be a grass (instead of sedge or rush)
I also think the type of habitat where this picture was taken is called "high marsh" (of the fresh water, tidal, mudflat variety)