Subnautica: Below Zero follows the adventures of a young ecologist who becomes stranded on an alien planet. While exploring these arctic waters, she receives an alien transmission coming from deep within the Twisty Bridges. Her curiosity will lead her to discover the mysterious Architect base known as Sanctuary Zero.
Finding the Sanctuary Zero base will be one of the earlier missions Subnautica players will be introduced to. The base is located deep below the spiraling rock formations of the Twisty Bridges. Starting from Delta Island, players should head to the Delta Station dock. The Seatruck can be crafted and used to conserve oxygen as players make their way towards the Twisty Bridges.
Once at the dock, players should head northwest of Delta Island. There is no need to dive too far down as the landmark players will be looking for is close to the water's surface. After having traveled about 350 meters from the dock, players should be able to spot a large, looping branch of the Twisty Bridges. Swim towards the structure, then descend straight down into the biome. Look for one of the Alterra tech sites.
Having reached the tech site, inspect the surroundings. Keep an eye out for faint, flashing green lights. These blinking beacons are the key to locating the Sanctuary Zero base. If players brought along the Seatruck, they might need to leave it here since the vehicle does not operate well at lower depths.
Players may utilize the Seaglider to continue their search from here onwards. After having located the beacons, players will need to follow the trail of flashing green lights through the network of underwater caves and tunnels. Make use of the oxygen plants scattered throughout the caves. If they keep on the right path, players will come to the entrance to the Sanctuary Zero base.
After entering the Sanctuary Zero base, Robin is introduced to Al-An, an Architect who warns her that the facility is in critical condition. He mentions that he requires a new host, or else he will perish. Robin will offer her PDA as a suitable space for Al-An to transfer onto; however, the Architect will misunderstand her offer and instead upload himself into her brain. Subnautica: Below Zero follows Robin's journey to construct a new, suitable vessel for Al-An so he can leave her head.
While investigating the base, players should be sure to pick up the three available Ion Cubes. These glowing, green crystals will be necessary for crafting tools such as Ion Batteries, the Tether Tool, and the Quantum Locker. Players will also be able to use them to construct the Architect Organs necessary for building Al-An's new vessel. To successfully construct his new body, players will need to craft the Architect Organs, the Architect Skeletal Structure, and the Architect Component (Tissue).
Subnautica: Below Zero is available for PC, PlayStation 4, PlayStation 5, Switch, Xbox One, and Xbox Series X/S.