This showed up on my google homepage and it's something I've talked about with customers from time to time over the last few years as it's something I read on the net back at least 3-5 years ago.
Watch the video first or I guess I'm giving it away... a few years back they started finding dogfish shark carcasses in the big display at the Seattle aquarium. Employees spent the night to see if they could figure out what was going on and a video showed up on the net, I'm thinking this is a re-edited version unless another public aquarium has had the same experience.
Back in the day when I dove off Newport, Oregon with my Instructor and his buddies, they'd come up talking about the octopus they'd found.... meanwhile, I saw nothing.... it was early in my diving days and I still had "tunnel vision" and more or less focused on what was directly in front of me. I remember one of them saying they found one they didn't even want to think about touching, that it might get too much of a hold on them. It appears these critters can be pretty darned strong.