Marsh gentian; catchfly prairie-gentian; seaside gentian (Eustoma exaltatum, Gentianaceae)
This was the largest group of marsh gentians I had ever seen. They can usually be found in small numbers along Blackpoint Drive in the Merritt Island NWR. The ones there are only a foot, or so, tall.
Also in the lock area was this low-growing plant. Perhaps the low growth was the result of repeated mowing. There were a large number of the plants, mostly along the edge of the roadway to the lock and along the chainlink fence, but also scattered about the grassy areas. The thread-like leaves should help identify it; however, I could not find a match in any of my wildflower guides.