Looks like it could use some teeth sharpening, those chompers just aren't vicious enough.
Never know if my name drop is good or bad.
I was just going through all the entries I gave a vote of 7 or higher to (seven entries) and reading the comments. This obviously was one of them. I really liked it because it was different. I only gave it a 7 because it was a little too OOF and grainy for my liking with regards to this subject and composition. I still found it much better than a lot of other entries though, good job.
Great idea. I don't know where you took this, for me personally the grunge effect doesn't work. I assume you wanted to give it a "Jaws" feel, it just doesn't work for me.