You don’t believe in magic do you? Magic is just make belief.
Devils pool is just a calm place right at the edge of one of the largest waterfall on earth. You can safely walk into the pool and be there. The currents are none and you are safe, although, you are pretty close to the edge.
Like with everything, there is no healing purpose or health benefits. Bathing is good for you I guess. But this is simply just a waterfall.
I am certain that some people have jumped over the edge or been drunk or something. But normally, this is very safe.