Subnautica takes place inside The Crater of an enormous, dormant, aquatic volcano, two kilometers in diameter. The Crater Edge is the area surrounding this crater. With no resources and extreme danger, the zone serves as a border for the game's map.
Three adult Ghost Leviathans live in the Crater Edge, where they deter players from straying outside of the playable area. When entering the Crater Edge, a single Ghost Leviathan spawns in at first. If the player stays in the Crater Edge for thirty seconds, a second Ghost Leviathan will spawn. Staying in the area for another thirty seconds will spawn a third and final Ghost Leviathan. They will pursue the player until they return to the playable area, upon which all Ghost Leviathans retreat.
Spoiler alert: The following section contains story related material.
The Crater Edge is said to only support two kinds of life, microscopic, and Leviathan class, meaning that prior to Kharaa's decimation of the ecosystem, this area may have been the natural habitat of the Sea Emperor Leviathan species.
The edges of the playable area, the Crater, stretch downwards to a depth of 1120 meters. At that point, the world cuts off on most ends. Underneath the Inactive Lava Zone and Lava Lakes, the map stretches farther to 1920 meters.
Once the player has gone 8,192 meters in any direction, the player reaches the farthest reachable point of the Crater Edge. Beyond this point, the player, as well as any piloted vehicle, will be teleported back to a randomly chosen location that is 10 meters above sea level and up to 250 meters away from the center of the map.
At approximately 4000 horizontal meters away from the map center, the zone ends. Leviathans cease spawning and there is only an empty ocean, acting as the real end of the game's limit.
Data Bank Entry
Geological scans of this area show a steep decline in all directions. This data is consistent with the theory that the Aurora crashed on the edge of a 2km x 2km volcanic crater. It has likely been millennia since an eruption reached the surface, encouraging the ecosystem within the crater to flourish.
The ecology of the trench surrounding the crater supports only two kinds of life: microscopic, and leviathan class. Exploration is ill-advised.
- Before the Big Little Update, Crater Edge used to have unfinished terrain at around 3000 meters depth. The bottom of the Crater was found here, which was a flat area that covered about a 2km x 2km. At 3040 meters depth, the world cut off. 
- Sea Dragon Leviathans, Reaper Leviathans, and other fauna were planned to spawn in the Crater Edge at one point, but this idea was scrapped.
- The Crater Edge was originally called The Void and the Dead Zone.
- The Crater Edge is the deepest biome in the game.
- The Crater Edge is one of the two biomes that do not harbor flora, the other being the Lava Lakes.
- Subnautica: Below Zero has a similar biome found on Sector Zero known as the World Edge.
This section contains bugs related to Crater Edge. Make sure to only post reproducible bugs, and use appropriate system template ( , , / ) depending on which platform(s) the bug has been encountered on.
- When swimming very far out from the playable area, the player's screen will appear to shake violently. This is likely caused by floating-point errors, meaning that the game is unable to accurately calculate the player's location.
- Only on consoles, the game crashes upon reaching 3000 meters in depth. The reason is unknown, but is somewhat consistent.
- https://www.youtube.com/watch?v=ivNIbotnHsU Dated August 9, 2018.
- https://unknownworlds.com/subnautica/subnautica-big-little-update-released/ Dated December 11, 2019.
- http://imgur.com/a/BSgYH Dated May 16, 2017.