MORGANA-151

Your shading is good, and your rendition of the light under the water is excellent and eye-catching.

The proportions are cartoon-ish, but that's OK in my book. I think that what you really need to focus on is the hair and the faces. I know hair isn't easy to do well, and your technique is fine, but I think hair is too big even for a cartoonish style. Maybe it's the look you're going for, but In my opinion, it's just too much.

Also, your faces need work unless if you want them proportioned like that. The eyes are a little too big (about 50% too large) and the cheek should be more puffed out. Remember, cheeks are convex, not concave. The ears are well done, and the noses are alright except for that line (which I assume is supposed to indicate change in angle) doesn't really need to be there. The shading already does the job. Maybe you could make the lips a little smaller, too. Just slightly.

Try giving the faces some personality. They both look like hardcore lesbians, maybe make at least one of them look more like a girl who's bi and just trying to have fun.

One cool thing that I like is the way their bodies are positioned. It's hard to tell from the thumbnail whether their bodies are bent double or straight, which reminds me of an optical illusion.

In my opinion, if you want help with facial proportions, Google some German girls. Their sculpted features and flawless bodies (not that they all look like that) are ideal.

I gave 4 stars for vision because this looks difficult to draw (i don't know what software you use).
4 for originality, because of the undersea backdrop and the positioning I mentioned earlier.
5 for technique, because I can't find anything wrong with it.
3 for impact, because the faces need work.

One more thing. I would lighten the skin color of the orange-haired girl, because orange hair doesn't look good against dark skin. Try making it a shade lighter than the other girl, and with a hint of redness. I wouldn't change the hair color because the contrast between the cartoonishly orange hair and the blue water works really well.

Alright. I hope that helps.