: A newly discovered underwater ecosystem that Ken, a professional diver, initially reports as containing human-like figures.

:If you are referring to a different show, S1E13 of these popular series often involve "deep" themes or titles: [Rewatch] Made in Abyss - Episode 13 discussion - FINAL

In the context of the animated series The Deep , is titled "The Abyss Stares Back" . Plot Summary

: Nereus reveals that the "hole in the sea" is mentioned in the ancient Chronicle of the Deep , which describes it as a place that hides deep mysteries.