Leviathan Class Organisms

Leviathan is a classification given to extremely large creatures. Although the wording of the Reaper Leviathan's databank entry would seem to imply that the leviathan classification is exclusive to predatory life forms, this is not the case; any fauna species of a suitable size can be classified as a Leviathan.

Leviathan is not part of a taxonomic classification so does not imply any of the species classified as such are related. In fact, the only two that appear to have any close relation are the Sea Emperor Leviathan and Sea Dragon Leviathan who share several features including an almost identical body shape, seven identically positioned tentacles, forelimbs and light producing organs protruding from their snouts.

Despite being enormous when compared to the fauna of Earth, the leviathans inhabiting Planet 4546B in the present day are dwarfed by their predecessors; the three-million-year-old Gargantuan Fossil at completion measured an estimated 6-8 times longer than a fully grown Sea Emperor Leviathan specimen. To support a predator of such titanic proportions, many of the other creatures of that time period must have also been similarly sized or larger.

Although the term "Leviathan" is used to refer to an aquatic creature in the real world, there is no confirmation on whether or not the Leviathan classification is restricted to aquatic fauna in the Subnautica universe, or is simply the term used for any species of a sufficient size.

Known Leviathan Class Organisms

 * Sea Treader Leviathan: Unspecified; smallest Leviathan
 * Reaper Leviathan: 55m
 * Reefback Leviathan: Around 70m
 * Ghost Leviathan Adult: 107m
 * Ghost Leviathan Juvenile: Around 65m
 * Sea Dragon Leviathan: 112m
 * Sea Emperor Leviathan: Around 160–200m

Presumed Extinct Leviathan Class Organisms

 * Ancient Skeleton: Size indeterminate
 * Gargantuan Fossil: Around 1200–1500m

Trivia

 * The Sea Emperor Leviathan is suggested to be the largest identified species in the Subnautica universe, at around 160-200 meters in length. Despite this, it is massively out-sized by the Gargantuan skeleton which would measure well in excess of one kilometer at completion. Due to the massive size disparity between the largest confirmed Leviathan and the Gargantuan, as well as the lack of any mention in the databank entry, it is unknown whether or not the Gargantuan would be given the classification of Leviathan, or perhaps a new classification for a creature of such extreme size that it exceeds the size of a Leviathan.