At first glance, her torso seems a little on the short side.
Granted, I don't know what kind of optical illusions a hot tub would have at such a camera angle. I know when scrunching low under the water when the bubbles are on the water does kinda create some distortion for sure. :P
So with that in mind, I either say 'initially it seems like the torso is too short in comparison to the rest of her body' or "I'm not a master of light and distortion and thus cannot accurately critique'.
Back above the water though:
Compositionally quite stunning!
A shiny piece to be sure, and I'm liking those reflections of the benches in the background along with the towel racks and candles along the wall.
The mirror on the left hand side of the back wall is dim and reflecting what I imagine to the be the rest of the semi-dark room, however the cloth with the symbols would have more light on it since the gold decals beside it are almost at full illumination.
If a doorway is shining enough light to light up the gold, there is enough light to have the blue on the cloth be more lit and vibrant.
The gold trim on the hot tub as well would be a bit more lit as well, since if Ena is practically fully lit from a forwards and/or downward light source, shiny gold would be well lit as well (as far as my knowledge on gold goes :P ).
Anatomically and stylistically speaking, everything else pretty much fits into the tone and look you were going for.
That said, the water of the hot tub, since it's calm and not bubbling should have a more refined edge for contrast and make it look a little bit less smudged.
The steam/fog effect is cool, but looking at how you were aiming to make the water look ultra still to match how little Ena is moving, a crisper edge would lock it all in.
(Keeping in mind I am not the foremost expert on lighting, so double check and ask around before thinking my suggestions are 100% sound)
Otherwise, superb work. :)