Early Game: Environmental O2 Sources
Increasing your O2 capacity is one of the most critical early-game priorities in Subnautica 2. Without adequate oxygen reserves, you are severely limited in how deep you can explore and which rare resources you can harvest. Managing your breath is not just about survival; it is a core progression mechanic that dictates your reach into the ocean's depths.
Before unlocking advanced gear, you must learn to utilize the environment. These methods are essential for extending your dive time without consuming precious resources.
Oxygen Tunics and Bloom Sap
Your first line of defense involves finding Oxygen Tunics. Despite their name, these are not wearable items but rather blue, blob-like organisms that release oxygen bubbles into the water. Swimming into these bubbles refills both your O2 bar and your Air Bladders.
Additionally, explore the environment for funnels blocked by Bloom Sap. Use your Survival Multitool to hack away the sap, revealing a column of bubbles. Hovering in these columns allows for a slow but steady refill of your oxygen reserves.
Air Pockets in Caves
When exploring underwater caves, keep a close eye on the ceilings. Air pockets often form in these enclosed spaces, providing a natural refuge. Dipping into these pockets allows you to refill your oxygen without returning to the surface, which is vital when you are caught in tight passages or pursued by predators.
Mid-Game: Permanent Upgrades
To truly expand your diving capabilities and learn how to increase O2 effectively, you need to craft and install permanent upgrades. These tools significantly extend your time underwater and improve your safety.
Oxygen Control Biomod
Once you have crafted a basic battery using an Acidic Raion Pouch, head to the Welcome Center colony ruins located southeast of your Life Pod. Inside, you will find a Biolab. By plugging in your battery, you can access the Biolab to slot Biomods onto your character.
The Oxygen Control passive Biomod is highly recommended. It drastically slows your O2 consumption while you are stationary, making it perfect for scanning organisms or investigating ruins without fear of suffocation.
Air Bladders and Standard Tanks
Air Bladders are versatile flotation tools that serve as a safety net for emergency ascents. You can craft them using the Fabricator with these materials:
- 2x Titanium
- 1x Rubber (crafted from 2x Lucifer Rotsacs in the Resources tab)
Consuming an Air Bladder partially refills your oxygen and propels you rapidly toward the surface. For a more permanent boost to your O2 capacity, craft the Standard Air Tank as soon as possible. This requires:
- 2x Titanium
- 1x Rubber
- 2x Silver
Silver can be found in locations close to the Lifepod, making this upgrade one of the first major milestones in your journey.
High Capacity Air Tank
For a significant boost to your oxygen reserves, you will need to craft the High Capacity Air Tank. This upgrade is more involved and requires specific prerequisites:
- Unlock the Sonic Resonator.
- Build a base equipped with a full Fabricator.
- Possess the Standard Air Tank.
Acquiring the Recipe: The recipe data card is located in a colony ruin southwest of the Life Pod. Head southwest over the ocean floor drop-off, skirt the wall to your right (passing hanging wreckage), and enter the ruined structure below you to find the recipe on a desk. Be sure to collect the Lithium found on a table outside the ruins as well.
Crafting Process: Build a Processor and switch it to Plasteel Ingot mode. Combine 2x Titanium and 1x Lithium. Finally, combine the resulting Plasteel Ingot with your Standard Air Tank at the Fabricator.
Late Game: Advanced Oxygen Management
As you dive deeper, pressure increases and oxygen consumption accelerates. Advanced gear is required to manage these conditions safely.
The Rebreather
The Rebreather does not increase your total O2 capacity but significantly reduces the rate at which you lose oxygen while diving deep. This tool is essential for exploring the deeper biomes. To craft it, you need:
- 1x System Chip
- 2x Fiber Mesh
You can find the scan data in a habitation structure built into the cliff face, just north of the colony ruins. Fiber Mesh is crafted using 2x Fiber and 1x Strong Acid, while the System Chip requires 1x Wiring Kit and 2x Quartz.
Portable Oxygen Generator
For extended missions, the Portable Oxygen Generator is a powerful tool. The first scan location can be found inside The Great Jaw, a massive, jaw-like structure near the colony ruins. Swimming inside this giant pod reveals the generator, offering a mobile source of oxygen for long-duration dives.
