Really love it, notice that your whitest is f7f7f7, maybe adding a little tiny bit of pure white ffffff in your white area will bring stronger light intensity above which you could use to help you notice the area where the light hit for you to balance it .

Another photoshop trick to bring about contrast can be the Layer->Adjustment-> Levels, the level adjustment layer, and when finish adjusting the contrast fill it with black fill bucket then use a white brush to slowly fill in area where contrast really matter.

Still an awesome painting though :3

Seriously man, how dare you not copy a reference photo exactly?

Good job, especially on the hair. If anything, I'd like to see you deviate from the reference more, but this is lovely and there's not much to improve on.

The realism in this is impeccable... I've neither attempted nor fathomed such a vivid piece depicting something underwater - a person, no less. Even though this was taken from a photo, it seems as if you have a solid understanding of lighting and depth.

I took a look at the website, and those are some beautiful art references; it's no wonder your piece came out so well. Having looked at the photo from which you derived this piece, however, I have a few criticisms:

Altogether, this seems very, very accurate, so it wasn't until I looked at your reference that I spotted almost any difference. The front of the neck and eyes of the figure where what appeared patently different upon comparison (namely that they appear to jut forward a bit in comparison to the stock photo); also, the mouth is a bit larger than that in the photo - something I noticed almost immediately; additionally, the hair is a lot darker than that of the photo - not to mention less voluminous - which makes quite a difference. In general, the piece has much more contrast in comparison to your piece. And, although I really don't want to try and criticize this (because it's obscenely beautiful), the water droplets at the top are a tad large in comparison (again, it's still obscenely beautiful); I also understand that making them that small would prove difficult in terms of adding detail to them. In brief - and I'm not to sound disparaging in any way: lighten it up, add contrast, and pay a little more attention to the stock photo.

Again, just to clarify, I think that this piece is amazing. Also, my criticisms were in no way a form of derision or contempt, but a form of constructive feedback; I hope you benefit from them in some way.