Over many generations, you evolve into a group of jet-powered, probably smell-driven hunters of the middle depths of the sea. Historically, some of your group were huge, taller than a human, but those species have died off, and now the biggest of you are the size of a football.

Your physiology only allows you to go about 800m deep, but that’s still a lot of volume.

You grow a hard beak which sits above your ‘tentacles’, allowing you to drag in and then crunch through smaller creatures’ protective shells, and eat them. You do have eyes, but the nautilus eye has never evolved to be as good as some other mollusc eyes, remaining a simple pinhole rather than a lensed eye.

You have one unique trait: despite being a relatively deep sea creature, you can be caught and dragged up to the surface without any injury. When placed back in the water you will just swim away happily, and very slowly descend back to the depths.

You are a Nautilus.