Lentic life

I've been trying to learn more of the wetland/edge plants this year, but very few of them stick, so I'm hoping that documenting them this way will fix that.  I believe this might be blunt spikerush, (also called a spikesedge)  Eleocharis obtusa , an American native. It's an annual with erect, cylindrical stems. Quite lovely! I think this is sand spikerush,  Eleocharis montevidensis, another native. It's more slender and less robust with a brilliant green tinge. It looked a lot like lawn grass from the water, and then I read (at the  Lady Bird Johnson Wildflower Center  site) that it is 'good as a lawn replacement for low, wet areas.' This spikerush is a perennial and spreads through runners.