This is an amazing pencil piece with enormous detailing that keeps me captivated for minutes on end!
I love the overall composition, things fit together nicely and I really like the faded effect of the fins and such to give the upper portion a softer look. This contrasts nicely with the darker, harder lines of the lower part. I do find the draping material across her tale a bit out of place though. It is rather distracting to me and disrupts the over all light to dark flow of the composition.
Her facial expression brings great interest to the piece as does the your overall style. It's an interesting mix of realism and slight cartoonism (is that a word? ha ha!).
I really love how her hair merges into seaweed and also the harder looking scales give a nice contrast to her softer human flesh.
As the other critique mentioned, I agree that the hands lack some detail compared to the rest of the piece, although they seem to match the rest of her anatomy in size and shape just fine.
Overall, I simply adore this piece and it is a great inspiration for those of us who are driven to capture the beauty and mystery in the many forms of mermaids!

I really love all the detail that went into this. Her tail, the coral background, and the seaweed all look wonderful. I also like how you chose to add the scales on her face. Most people have such an idea of mermaids being Arial beauties that they end up leaving out most of the fish details, so it's nice to see the aquatic influence applied more heavily here.
Each time I look at it, my eyes drift to the expression; I find it very interesting. She looks rather upset, and it leaves me wondering why. You did a great job on the face overall.
It does bother me how the hair sort of blends into the background. I feel this could have done to stand out more. I can see that her hair morphs into seaweed at the ends, but it doesn't jump out at you as immediately as it should. Instead, my eye follows it to the shell and then I sort of wonder where it went.
Another thing that bothers me is her hands. They're very stiff and don't look as natural as they should.
I really like this picture and the time and effort you put into it show through in the detail and overall quality. I look forward to seeing more of your work.