In my personal experience, I've seen many creatures in both conceptual and realistic form. The vibe this gives off is a carnivourous crab that is the love child of the Kracken and a turtle. I can honestly say I never saw that coming. XD
I personally liked the tripod concept, it gave it a nice unusual feeling. I would highly suggest looking into more marine life if you want to make this epic. More details on the shell could be nice, as well as a possible weak spot. You're really starting to get better at concept art.
Lol, that is an awesome interpretation of this Thank you very much. I'll look into some more marine pictures, I only looked around so that I can get an idea for the head/face. And also, the underbelly is it's weak spot, though I see it doesn't look very clear in this