Umibouzu
Umibouzu (海坊主, "Sea Priest") are water youkai that show up throughout the GeGeGe no Kitarou series.
These creatures are massive and dark-skinned, though most of their bodies stay submerged so their full appearance remains a mystery. They do have at least one visible left arm. Their faces are pretty simple—just large eyes with white sclerae, black irises, and white pupils.
Interestingly, some umibouzu are thought to be humans who transformed into mermen or youkai at some point.
In the 2018 anime specifically, they're rendered with black, rubbery skin and no hair. They're depicted as huge, with most of their bulk underwater, though they clearly possess a left arm. Their faces follow the same basic structure—large eyes with light blue sclerae, black irises, and white pupils—but their mouths are distinctly squid-like, cylindrical and grey at the lips.
Content compiled by AnimeList.moe from publicly available sources.
