there are a lot of guapote, which are the central american large cichlids, dovii, etc...that have been found, in Costa Rica in Salt water, there was a TFH article on it with pictures a few years back.
Also, I've heard first hand from a friend/biologist down Brazil that found stingrays, arowanas, and pacus in a landlocked salt water lake, oscars breeding, until the rainy season hits and they're able to move out.
down in new orleans we see them in the wild hunting in saltwater lakes it seems to be mostly a late spring and summer thing.we have measured some over 5 close to 6 feet.