Overall this is a very nice peace which reflects lots of potential for easy improvement in future works.

You show an incredible sense of lighning with this work, which is not an easy thing to do when the character is in a dark environment.

The textures are also pretty good. Usually most of the works we see of mermaids show a uniform textured tail or 2 parts completely different from each other that seems we copied some random material and pasted there (I can tell, made this mistake in a work of mine ), which you didn't do here: we can see that the last part of the tail (sorry for my lack of english technical terms ) is really thin and fragile, though it's still consistent with the opaque part of the fish tail.

Also, you created here a clear context of movement, not only with the floating meshs of hair, but also for the pose choice, as well as the bubbles near the tail.

Maybe you could have chosen not to paint so many meshs of hair, though, or maybe to concentrate them more in one of the parts of the painting. I feel the hair is getting more attention than the action or the character herself - her left arm is a little bit hidden from it and it gives the impression that the anatomy of her chest and right arm is not correct, which is not true if we look carefully. Also, I think you are perfectly able to do more realistic bubbles than those.

Anyway, keep up the great work!