Many who make alien creatures got lot of imagination, but make creatures that would not work in reality - and so end up less believable. Yours do work though, and I think you've had a look at some species of amphipoda when you made this one. And with the weird creatures during the Cambrian age something similar might even have existed. So crit? Ok I crit you with a full score here.
I like the overall design and the coloring is beautiful, the only thing that throws me is the mouth. Admittedly this is more a point of preference but the mouth looks really reptilian (or eel like) while the body a crustacean and it creates a bit of biological dissonance in my mind. Overall beautiful piece.
The design of the creature is very nice, but the preview of it tells me it's about the same size as a lighter. There is no water between it and viewer or any similar effects to give viewer any sense of how large this creature is.
Amazing as usual I agree about the lighting though,,, you can take it another way with making more deep sea to where doesnt reach but then you would need to make him glow... you should play around with it and always go what is right for you... I think it either way it is amazing