I'm sorry but it looks like fake, if you look closely at the near end of the video, there are some problem with the shadow, color, contrast and displacement on the video letting me think it's a CGI
It does make you wonder what else might be down there in the depths of the oceans.
What a beauty.That's a cephalopod, you can clearly see its true form near the end before it escaped into a plume of ink.
edit, perhaps it was two of them (mating?) and split near the end (two forms can be seen, i thought it could be ink but it didn't plume).
They often have bioluminescent nodes on their tentacles (the deeper and darker, the more 'alien' the species since they can flicker and flash any possible color).