Hadal

Hadal ( HEYD-l ) pertains to 

• the greatest ocean depths, below approximately 20,000 feet.
• the bio-geographic region of the ocean bottom below the abyssal zone.

The word comes from the name Hades, the Greek god of the underworld.

So in the movie, The Abyss, Sam Harris has reached the "hadal" level of the ocean. Fantastic scene, indeed! But has he met Hades down there? Nah, I don't think so but he has certainly met something "not-like-us" down there. I like that movie, one of my faves!