Arapaima

The arapaima is a large fish that is native to the amazon river. Adaptations that the modern day arapaima has include powerful jaws, a modified swim bladder that allows them to breathe oxygen, and incredibly tough scales to protect from predators. Their future habitat would likely be a more polluted amazon river however, due to their swim bladder, they should be able to survive without needing to completely filter polluted water. Seeing as arapaima have existed for millions of years, it is unlikely that they will change very much in the next hundred or thousand, the most likely changes would be a duller coloration to provide even more camouflage as well as disruptive coloration to make their form harder to distinguish in their native habitat.