I think this is the only picture of this species on-line.It is protected by the Mexican law. very rare restricted to rivers and swamps.Esta es otra especie de la misma familia y gnero:Lirio menor limoso (Heteranthera limosa)
Tribonanthes brachypetalaThis is a plant which over the years, I thought was disfigured, because it didn't have showy petals. This is how it grows with short yellow petals and long reflexed bracts. It is quite attractive if you stop and look.