Literally the worst thing in subnautica

Solarpunk is a movement focused on a positive, ecological vision for a future where technology is used for human-centric and ecocentric purposes. It is a literary, artistic and aesthetic sub-genre and is also closely tied to eco-political activism. Solarpunk narratives have a distinctly positive and utopian foundation in contrast to the often dystopian visions found within other "punk" science fiction genres.

The Ghost Leviathan is one of three hostile leviathans in Subnautica.
It is most likely the second one you'll encounter unless you enter the void.
There are 2 types of ghost leviathans. Juveniles and adults. They can be spotted in the Lost River, Crater Edge, Grand Reef, Bones Field, Ghost Forest, Mountains Corridor, the Northern Blood Kelp Forest, and the void.
Both types of Ghost Leviathans are very dangerous at melee range.
There is a Reference to the Ghost Leviathans called the Eidolon Wyrms