Cascade Creature

You may think what you see at 20 seconds into the video below is just a little jelly fish. But wait — you‘re about to be taken on a ride where you’ll see it grow, morph, undulate and still won’t know quite what this confounding, “easily the most insane animal footage ever caught on an undersea camera” is.
As the film rolls on, the creature appears to be getting bigger. At 57 seconds what you saw flash by at the beginning of the footage reappears. Things start to get even more visually interesting when an organ of the creature (or perhaps it’s dinner inside its gut) comes into view around 1:51. At this point, you also have a better view of the texture and pattern of the filmy organism’s exterior
It’s hard to tell if it is moving itself or is dead and simply moving based on ocean currents.
Reddit users have poured over the topic with suggestions as to what the creature could be ranging from a plastic bag to an alien to a whale placenta to the more plausible jellyfish. The Huffington Post reports it could very well be a Deepstaria enigmata jellyfish:
According to the Marine Species Identification Portal, the Deepstaria enigmata is found in the South Atlantic Ocean, with a bell that can measure up to 60cm in diameter.

It has “oral arms” which end in “curious hook-shaped organs.”

Underwater Footage of Creature Suggested to be Jellyfish With Curious Hook Shaped Organs.

This type of jellyfish is “imperfectly known” because specimens of it have been damaged. It is unclear where this original footage was actually taken, but according to the timestamp, it appears to have been recorded on April 25.