Subnautica: Below Zero is a survival adventure game set in an open world environment and played from a first-person perspective. The player controls xenologist Robin Ayou, who lands on ocean planet 4546B in pursuit of answers about her sister's disappearance. Like its predecessor, gameplay involves exploring and surviving in alien environments while also completing objectives to advance the game's plot. Players collect resources, construct tools, build bases and submersibles, and interact with the planet's wildlife.[1]
To survive and progress, the player must collect raw materials from the environment, including various minerals, flora samples, and fish, while avoiding or countering threats like hostile fauna and blinding snowstorms. They must also acquire blueprints to craft new items, either through finding and opening databoxes in the world or by scanning fragments of the item. Generally, the player must face harsher environments the further they progress, requiring better equipment or upgrades for old ones, like suits that resist the cold, oxygen tanks with higher capacities, or vehicles that can withstand deeper waters.
The game primarily takes place underwater, but, unlike its predecessor, there are much more expansive and dangerous land-based areas to explore. There are structures and wrecks to find both above ground and underwater, which serve as key locations for the story, providing blueprints and recordings of conversations that slowly reveal lore.
Alongside returning mechanics such as oxygen, hunger, and thirst, players now have a body heat gauge which comes into play when walking on land. It functions much like the oxygen gauge does underwater. The player will gradually lose body heat and freeze unless they replenish their body heat by jumping into water, finding shelter, consuming certain items or standing next to a heat source.
Upon beginning a new game, players must select a difficulty mode from the following five:
Survival — The player must manage health, hunger, thirst, oxygen and temperature. Upon death, they respawn, but certain items are lost from their inventory. This is the "standard" game mode.
Freedom — Just like survival, but with hunger and thirst disabled.
Hardcore — Survival mode with permadeath. If the player dies, the player will not respawn and their save file is deleted.
Creative — Health, hunger, thirst, oxygen and temperature are disabled, all the crafting blueprints are available at the start, and no resources are required to craft. Additionally, the submersibles, a Seaglide, mobile vehicle bay, knife, flashlight, habitat builder, scanner and a propulsion cannon are provided. They do not need an energy source and cannot be damaged (unless the player damages them intentionally).
Custom — Various options are given to customize the game, such as weather, day and night length, creature spawn rates and aggression, etc.