In Subnautica 2, players often face challenges due to limited oxygen supplies while exploring the ocean's depths. To enhance oxygen capacity, players can utilize various environmental features and upgrades. Natural sources like Oxygen Tunics, Bloom Sap, and air pockets in underwater caves provide essential oxygen replenishment. Upgrades include the Oxygen Control Biomod, which significantly lowers oxygen consumption, and several types of air tanks. The Standard Air Tank increases oxygen reserves from 45 seconds to 75 seconds, while the High Capacity Air Tank extends this to 120 seconds. Crafting these tanks requires specific materials, including Titanium, Rubber, and Silver. Additionally, the Rebreather, although it does not increase oxygen capacity, reduces overall oxygen consumption, allowing for longer dives. Players are encouraged to explore wrecks and complete missions to unlock these essential upgrades, ensuring a more successful underwater adventure.