Unigenes humifusa by the water's edge

By water, partly hidden from the sun among reeds, Unigenes humifusa flowers diligently. When the corolla goes, the small calyx lobes, the sepals, extend above the fleshy ovary topped by the persistent style.

This herb looks like a Lobelia, once was a Lobelia, and forms part of the Lobeliaceae family. See what is shown about it in the Herbs Album (Bean and Johns, 2005; Bond and Goldblatt, 1984; iNaturalist).