Rambling through YouTube you find some strange stuff, but this is a real creature caught on film during an apparent underwater inspection which apparently approached the camera and then swam off.
God has created things we could never imagine in places we might never see – I am in awe!
Meet “Deepstaria enigmatica, a jellyfish of the family Ulmaridae.” Further individuals later have suggested the species is actually “Deepstaria reticulum.” An interesting jellyfish, nonetheless.
Here is the website that goes into full detail of the event, including stills with descriptions of what you are seeing in each: Placental Jellyfish.
I wanted to copy the whole thing, but that would have been completely redundant. It is pretty cool, eh?