This piece of work contains no 3d geometry. By procedurally created 6 set of textures, 6 planar planes are displaced by height maps to form this water pistol. I have similar works like this but this time I made the displacement system like "plastic injection molding" with thickness. So the best way to show this, was defining a material like translucent plastic shell.
This time I recorded and explained the process from scratch where you can find this 5 hours tutorial on my Youtube Channel.
https://youtu.be/HMnfJsB_4WU
You can find a similar project which is an handheld game console:
https://www.artstation.com/artwork/zxQYZL