You start Subnautica 2 with 20 inventory slots, and that cap fills quickly once food, water, basic tools, and crafting materials all compete for space. The game does not let you craft a bigger backpack or buy slots from a vendor. Instead, expansion is tied to exploration on the desert planet Zezura, where abandoned colonist bases hold the only objects that permanently grow your carry capacity.
Quick answer: Find an abandoned base on Zezura, interact with its biobed, and wait for the prompt “Endurance adapted. Inventory expanded.” Each biobed grants three permanent inventory slots.
What a biobed does
A biobed is an interactable medical-style fixture placed inside the abandoned bases left behind by previous colonists. Using one triggers a one-time character upgrade that adapts your endurance to Zezura’s environment and adds three slots to your personal inventory. The change is permanent for that save, applies immediately, and stacks across every biobed you activate at different bases.
Each biobed can only be used once per save. Returning to the same base later will not produce another expansion.
Requirements before you start hunting biobeds
You do not need a specific blueprint or crafted item to use a biobed, but you do need a way to reach the bases and the means to find them efficiently. The bases sit across a large map, and several are tucked into biomes that require oxygen, lighting, and basic mobility gear.
| Requirement | Why it matters |
|---|---|
| Scanner | Scanning items prompts Noa to send black box coordinates that lead to abandoned bases. |
| Oxygen tank upgrade | Several bases sit deeper than starter lung capacity allows. |
| Charged batteries | Scanners, flashlights, and the Tadpole submersible all draw power during the search. |
| Tadpole or other vehicle | Cuts travel time between distant base locations on the map. |
How to find abandoned bases on Zezura
How to confirm the upgrade applied
Two signals tell you the expansion worked. The first is the in-world message “Endurance adapted. Inventory expanded” that appears the moment you finish using the biobed. The second is the inventory grid itself. Open it with Tab and count the slots, three new squares should be visible compared with your previous total.
If neither signal appears, you either interacted with a different fixture inside the base or that biobed had already been used on this save.
Tips for managing inventory while you search
Because each biobed only adds three slots, the early hunt is the hardest part of the game for inventory pressure. A one-room base near your spawn with a few storage lockers solves most of the load problem, since you can dump non-essential materials before each expedition and only carry tools, batteries, food, and water on the trip.
Vehicle storage also helps. The Tadpole comes with a built-in storage slot by default, and larger craft can carry additional modules, so you can stage resources inside the vehicle while you focus your personal slots on items you need in hand.
Inventory growth in Subnautica 2 is gated entirely by exploration, not crafting. Every biobed you reach is another permanent three slots, so prioritizing the black box trail from Noa is the fastest route to a comfortable carry limit.
