Good job, but it seems a little 2D as a bust. I like the detail, though especially the accurate fin. I think you might want to make a longer head. You might be able to make a helmet if it is hollow, LOL. Overall, sweet bust!
It looks like it was hard to make, I am not really fond of the front of the head, but the back looks okay. I just think it looked a little bit flat. The black mask on the front was good though. ~Waff