There are native reeds in NA: " three separate lineages occur in North America – one endemic and widespread (the native), one from Europe (the introduced invasive), and one whose nativity is currently unclear which occurs across the southern U.S. from California to Florida and into Mexico and Central America (the ‘Gulf Coast’ type)." https://bugwoodcloud.org/mura/mipn/assets/File/Educational Resources/Phragmites Field Guide.pdf

They could probably find a native cordgrass and plant a perimeter of it around the pool to pretty decent effect I’d say.