In Barotrauma, the Abyss is defined as the layer of the ocean from 1600m depth and deeper, until the bottom of the levels. The pressure there is such that diving suits offer no adequate protection, and even the hull of the submarine take continual damage while in this zone; the deeper the submarine is in the abyss, the faster it breaks. It should be noted, with adequate protection of the hull, most submarines can survive up to depths of ~2000m before flooding. Past these depths multiple walls on the outer layers are advised, and all windows should be replaced with walls. Additionally, heavy ordinance such as Nuclear Shells should be brought in high quantity, preferably filled with explosives.
For obvious reasons, it is recommended to avoid going to these depths at all, much less diving in them.
Critical Depth[edit | edit source]
Depths below ~2500 are commonly referred to as "Critical Depth", where at any moment, the submarine may spontaneously implode, destroying nearly all structures in the sub and killing most of the crew. The most notable sign that you are approaching critical depth is when all the exterior lights on the submarine begin to flicker, then shatter. For this reason, submarines designed for deep-Abyss travel should always be fitted with exterior lights, as well as extra layers of hull. If intending to explore critical depth, players are advised to move the submarine slowly, as hull breaches occur more often when moving quickly.
Contrary to popular belief, the Abyss does have a bottom - if a submarine goes far down enough, it'll encounter the barren sea floor. However, there is nothing to be found here. The sea floor is mostly useless, as it lies far beyond critical depth, further than any ship will be able to survive unharmed.
While most maps' abyssal depths and critical depths are at 1600-2500m, the actual depth of these varies on the size of the map - if a map forces you to navigate lots of vertical caverns, the abyssal depths and critical depths will be deeper than usual; whereas if a map forces you to navigate long, horizontal caverns, the abyssal and critical depths will be higher.
Creatures[edit | edit source]
Despite the intense pressure of such an environment, the Abyss is not totally unlivable, as it is home to three different creatures: the quick and deadly Coelanth, the bulky yet fast Charybdis and the apocalyptic Endworm. Luckily, each of these powerful creatures are uncommon even in their home environment, and are almost nonexistent above the Abyss.
These creatures all have something in common: minmaxing.[note 1] For example, while the Coelanth is fast and powerful, its health is such that it can be defeated with five shots from a mere Harpoon Gun. Even the mighty Endworm will only ever notice submarines, and is the same speed in water as the player.
This means that, essentially, each Abyss creature is skilled at many things, but each has their own weakness.
Rarely does a mission force players to surpass abyssal depths, let alone critical depths, however it is entirely possible for both to occur.