I saw a freshwater stingray in a Florida river once. It was in a national park area and I asked the ranger about it, and he claimed not to know anything about freshwater stingrays. I also looked on the internet, and the only ones I could find were from South America. I still don’t know if it is native, or an invasive species someone dumped there.
My son was diving in the Chipola River in NW Florida, about 60 miles from the Gulf and saw a “sting ray”. He supposed it had just swum up the river.....didn’t mention that it could have been a freshwater ray.
Stingrays tolerate brackish water pretty well......