This Lego Nautilus is created by Mitsuru Nikaido. Specifically it is a Mecha Nautilus Mk2-10. This robotic sea creature features a grey and white color palette, there is no color here. The design is amazingly complicated. A system of clips and hinges create the spiral shape, and a whole lot of white plates protect it from harm. There are some surprising Lego pieces to be found. A part of an airplane jet engine is used for the top of the Nautilus, a few Bionicle pieces are around the top, and a Hero Factory logo/icon piece is used for the eye. The tentacle/feeler propulsion system looks especially good. The end result is a very organic Mech, kinda like something you might find in Horizon Zero Dawn.
You can see more of this Mecha Nautilus Lego MOC over here: https://www.flickr.com/photos/142497481@N02/50066737048/