I have this plant growing in my pond and am trying to identify it.
My first guess would be one of the aquatic cresses (of the mustard family, Brassicaceae), probably Nasturtium officinale. Unfortunately, the leaves of those species can be highly variable. Keeping that in mind, check the written descriptions at https://nas.er.usgs.gov/queries/FactSheet.aspx?SpeciesID=229 and https://plants.usda.gov/core/profile?symbol=NAOF. Does that seem to fit with what you can observe in the field?