The Hadal Snailfish mermaid is one of the deepest mermaids ever recorded. The cold, high pressure waters allow her to keep her adorable shape as she hunts for tiny sea bugs in the muck of the darkest part of the ocean.
This is one of the many mermaid species humans have never seen in person. Instead, information and illustrations are ferried to the surface by vertical migrant mermaids. Scholars, mermosologists, and diplomats bring communication through the different zones of the ocean. But those who travel the furthest vertically must know the most languages.
Humans who wish to learn mermaid languages will usually stop at Pelagic, since most mermaids they encounter will be surface-dwellers. They may be able to parse Mesopelagic as well, as it is closely related. But as one travels deeper, the languages of the oceans change and twist until they are formed of sounds a human can barely comprehend, much less speak.
So if you wanted to be a penpal with a snailfish, you would have to dedicate years to learning Hadal... or hope your courier is an accomplished translator.












