Not too much to say… I’m satisfied because is one of my first sculpture but the result is too simply and empty. How can I continue? Any suggestion, hint, advice (and so on…) are appreciated.
Thank you very much 
Maybe try and think about how the thing propels itself… maybe the side flippers need to be articulated like turtles flippers. or maybe some more developed jawline would convince us that it could eat big stuff. Have a look at some pictures of some underwater beasts and try and think why they look like they do.
If you are really stuck share the file and someone might give you some options.
It 's a nice feeling having sculpted something isn’t it!
Thanks for your reply, it’s a good analysis. I certainly take your suggestion in mind.
i should smooth the object and increase the hard edges.
just take a look at (z brush) alpha brushes https://i.pinimg.com/originals/28/d2/6e/28d26eac7cc44e631f6f0361e401bdd2.jpg
Of course, I didn’t smooth it because I would add more details. Thanks for the brushe tip 