It's blobby, doesn't have any clear defined shapes. Instead of making everything smooth and round, add some interesting shapes here and there. And like Andrew said, take note of the anatomy of real animals. Such as the inset fins, and that their mouths are 'longer'.
My sharkology (not a real word) may be off, but I think that's a Mako Shark. Here is some more ref for the front fins. In these you can see the fins inset more into the body of the shark and there is more detail in the gills as well. (of course those can be tackled with normal maps) This is just a kickass picture I found a…