Name of creature in the ocean that looks like it has a shell but also has tentacles that looks like a Pokemon?
I’m going to take a guess that you’re talking about a nautilus?
Nautiluses are super cool!! They’re the oldest living subclass of the cephalopods, and really haven’t changed all that much since the late triassic! Their ancestors were called ammonites which appeared waayyyy back in the devonian period (419.2–358.9 million years ago). I had a whole post on ammonites a long time ago which you can find here: http://squidscientistas.tumblr.com/post/124712468719/firstly-you-guys-are-awesome-and-i-love-this
Nautilus shells are composed is many gas chambers and as it gets bigger the nautilus will close off one of the chambers and move its body into the next one.
The wikipedia article on nautilus is super in depth and helpful so if you want to know more, check it out! https://en.wikipedia.org/wiki/Nautilus