I suppose in essence there is hardly a true difference between "natural" and "supernatural". Both just terms coined by Humans in their limited perspective having physical bodies.
People have a hard time understanding or believing that other entities could hold form and exist and think without a fleshy shell to reside in.
It would be easier to draw a line and guess what supernatural means to a Human, something which cannot be consistently touched or seen with the naked eye.
You can see plants animals, rocks and other people. However you cannot SEE air, but it exists, it is natural, so maybe that isn't sufficient.
Even more specifically what is considered natural? Something organic, and made of matter? Well, light is natural, and comprised of Photons.
Many "supernatural beings" are also comprised of such Photons. (electricity and magnetism included)
So IMO most things are Natural. I'd have a hard time finding something I could even classify as Supernatural.
Hope that was an okay answer!