Oxygen is the hard ceiling on every dive in Subnautica 2. You start with just 45 seconds of air, which barely covers the shallows around your Lifepod, let alone the deeper biomes where the useful materials live. Raising that ceiling is the single biggest quality-of-life upgrade in the early game, and the path to a 120-second maximum runs through a small set of craftable tanks, a few helpful plants, and one emergency bladder.
How the oxygen meter works
Your character starts with a base capacity of 45 seconds of breathable air. That number doesn't change on its own. The meter only grows when you equip a tank in the paperdoll slot, and tanks stack their bonus onto the base value rather than replacing it. Surfacing or entering an oxygenated base instantly refills the meter to whatever your current maximum is.
Two things refill oxygen without a trip to the surface: contact with Oxygen Tunic plants while submerged, and using an Air Bladder, which trades its stored air for an immediate top-up. Neither raises your maximum, but both buy you time on long dives.
Craft a Standard Air Tank first
The Standard Air Tank is the first real upgrade you can reach, and it adds 30 seconds to your maximum, taking you from 45 to 75. The bottleneck is Silver, which appears in ore deposits scattered around the shallow biomes near the Lifepod. Scan with the habitat scanner once you build a base, since a Scanner Station inside a base can pin Silver and Lead locations directly on the HUD.
Step 1: Gather Silver and Titanium from broken metal salvage and ore nodes near your Lifepod. Keep collecting Silver whenever you see it, even before you need it.
Step 2: Return to the Lifepod and open the Fabricator. Build the Standard Air Tank under the equipment menu.
Step 3: Open your inventory and drag the tank into the paperdoll slot. The oxygen bar will visibly extend, and the maximum value in the HUD updates immediately.
Tank tiers and total oxygen
Higher-tier tanks replace the Standard Air Tank in the same slot, so you don't stack them. Each tier raises the maximum further, and the top tier in Early Access pushes the meter to 120 seconds.
| Equipment | Max oxygen | Notes |
|---|---|---|
| No tank (base) | 45 sec | Starting capacity, cannot be increased without equipment |
| Standard Air Tank | 75 sec | Requires Silver; first major upgrade |
| Higher-tier tank upgrades | up to 120 sec | Crafted from deeper-biome materials at a base Fabricator |
To reach the higher tiers, you'll need a Fabricator placed inside a built base, not the one in the Lifepod. The Lifepod's unit is flagged as not fully functional and won't craft the advanced equipment lines.
Refill oxygen during a dive
Raising the maximum is only half the equation. The other half is buying back seconds while you're already underwater, which lets you reach material nodes that sit just past your current safe range.
Oxygen Tunic plants
Oxygen Tunics are bulbous blue plants found across the early ocean floor. They periodically release a cluster of blue bubbles. Swimming through that bubble cloud refills your oxygen meter without needing to surface. Tag the locations of Tunic clusters on the way out so you can route your return through them.
Air Bladder
The Air Bladder is an emergency tool crafted at the Lifepod's Fabricator from Lucifer Rotsac and Titanium. Activating it instantly restores about 20 oxygen, and it automatically refills its own charge each time you surface. It also pulls you upward when deployed, which can save you from drowning in a deep ravine but will interrupt whatever you were doing.
Get oxygen back at your base
Once you've built a Habitat Builder and placed a base, the interior counts as breathable air space as soon as the base has power. Walking inside refills your meter to its current maximum the same way the surface does. A base placed near a dive site effectively extends your useful oxygen window across an entire run, because you're never more than a short swim from a full refill.
How to confirm the upgrade applied
After equipping a tank, check the oxygen number above the meter on your HUD. It should display the new maximum (75 with a Standard Air Tank, scaling up with higher tiers). If the number still reads 45, the tank is sitting in your inventory rather than the equipment slot. Drag it onto the paperdoll outline labeled for tanks, and the HUD updates the same frame.