Small diving duck, I thought it might be a pied-bill grebe when @neomyte, who spooted this specimen, told me it was a diving duck, (I could not see the specimen well when I took the pictures. After watching for awhile, it was clear that the diving behavior was different from a grebes. Unlike grebes, which dive, stay under a while, and then pop up a distance away, this specimen would take a dive and pop up much more quickly and not far from the location where it first went under. Pictures 2 and 3 are part of the diving sequence, with picture 2 being the duck on the surface and picture 3 appearing to be mid-dive with wings outstretched on the way down or back up. I don;t picture 3 is a splash of water. The dive did not seem to create strong surface ripples.
See also https://www.inaturalist.org/observations/146644511, a picture taken earlier nearby of what may be the same duck in slightly better clearer light.
DFW City Nature Challenge 2022. Haley's moth night at North McWhorter Creek at the Lewisville Lake Educational Learning Area
DFW City Nature Challenge 2022. Haley's moth night at North McWhorter Creek at the Lewisville Lake Educational Learning Area
DFW City Nature Challenge 2022. Haley's moth night at North McWhorter Creek at the Lewisville Lake Educational Learning Area