Crater Edge

The Dead Zone borders the entire map of Subnautica. It is the area beyond the crater of an enormous, dormant, aquatic volcano, which is where Subnautica takes place.

The Dead Zone is the end of the map and has a small amount of unfinished terrain at 3000 meters depth. Past that terrain there is another, seemingly infinite drop.

Multiple adult Ghost Leviathans live in the Dead Zone, where they act as a deterrent for wandering players going outside of the playable area.

The Dead Zone  is said to only support two kinds of life, microscopic, and Leviathan class, meaning that prior to Carar's decimation of the ecosystem, this area may have been the natural habitat of the Sea Emperor Leviathan species.

Description
True to its name, the Dead Zone is a large open ocean devoid of any flora, coral, and all but one fauna species.

Fauna

 * Ghost Leviathan

Trivia

 * Sea Dragon Leviathans, among other fauna, were planned to spawn in the Dead Zone at one point, but this idea was scrapped.
 * The Dead Zone was originally called the Void.