Black Bounds

Black Bounds (ブラックバウンズ, Burakku Baunzu) is a Japanese manga series written and illustrated by Iyasumi Horide.

Plot
The deep sea bottom... high water pressure, darkness, low water temperature...

Livitina, a woman wearing a jet-black suit packed with lost technology, a her partner Jack, a shallow sea folk, look for artifacts from the ancient humans who conquered the dangerous abyss.

Passing through the threat of humanoid monster "ghosts" wandering on the sea floor and wild deep-sea creatures, can they escape the "lowest world" and bathe in the warm "sunshine"?