Comparing the two, they don't look like each other at all. Blanket Octopus: Please Register or Log in to view the hidden image!
I think it's a dead something-or-other. Internal organs (I think) show up around 4/5 of the way through; seems like an octopus that's had the mantle and head removed by something. That or the stalk-ish thing visible indicates it was sessile, whatever the hell it was. Fairly big though. I'll go with blanket octopus that has met its maker.
I would agree with that analysis. You can see at around the 4:45 mark where the mantle and head should be. Please Register or Log in to view the hidden image!
The video was made in 2012. You would think the creature would have been identified, and it has. It's called Deepstaria reticulum and is a jellyfish.
The "massive" part is an illusion. These jellyfish are about 30cm fully grown. There seems to be some disagreement about the species although it's a Deepstaria (I wonder if that name is related to the name of an oil rig somewhere?), it's also been labelled D. enigmata.
