cheers for the comments. Yes 'With Teeth' is taken from the NIN album title :) That fish reference is cool, I had been using a lot of deep ocean fish as reference but mixed up a lot of elements. I also did struggle with having the 'fish' appear underwater, ie transparent atmosphere in front of it, but also having it pop…
The curves of the body, especially near the tail, seem a bit disjointed. Perhaps a few more segments along the body would help give more natural, flowing curves. For the head, you might want to look at some armored fish like the dunkleosteus.