Probably not the correct species but it is the only yellow aquatic species on iNaturalist in Ecuador. I’m sure someone will correct me. Found in a shallow pool at the edge of a black water lake at the side of a large laguna off the Cuyabeno River. Please note the vegetation photo may or may not be associated with the flower. No aquatic vegetation was visible at the flower and the plant portion was only seen in the vicinity of the flower. Best I could do.