Not a million miles away from you-know-where.
It’s worth reading the story. You know, just once. How long you spend is up to you, but I’d suggest maybe a little over a quarter of an hour.
First glance, looked like sperm. 
Kinda like spermy little Plecos.
“–Japanese fisheries immediately began researching the feasibility of a 5-mile-long bottom trawling net.”
Surprising - they look not much different from what you might see in a living room aquarium. They’re five miles below the surface yet still have two eyes on opposite sides of their head?
Deeper than the Marianas Trench? We visited there in 1960. Hung around for twenty minutes and didn’t see any fish so we left. Haven’t been back.
Chances are that, like many cave fish, their ancestors were sighted and they have retained the eye structure because there’s no pressure to remove it although probably with little or no functionality.