The one in the last video looks like it's swimming by flapping its arms. That's pretty nuts if it's not just for show.
Edit: if you like floofy cephalopods, you might enjoy this video of a dumbo octopus and some goofball scientists: https://youtu.be/GlvGCTpp1tM
I feel like this is one Oatmeal comic away from internet fame. I can't think of any other source of viral Cephalopod memes. That is where I learned all about Tardigrades and Mantis Shrimp.
I'm a little sad mimic octopuses didn't take off as a meme. https://xkcd.com/928/ I still think they have great potential.