Multiplayer At a Glance
- Party size
- Up to 4 players (you + 3 friends)
- Mode
- Online co-operative
- Cross-play
- Yes — across all PC and Xbox platforms
- Solo
- Fully supported; designed to work perfectly alone
- Conversion
- A solo save can be opened up to co-op at any time
- Progression
- Shared across the party
Single-player first, co-op optional
Unknown Worlds has been explicit that Subnautica 2 is crafted as a single-player experience that you can optionally play in online co-op. The intent is that the game works perfectly solo and the co-op layer is additive — not a separate mode that hollows out the solo campaign.
Up to four players, with cross-play
A session supports a party of up to four. Crucially, co-op is cross-play across every supported platform — PC players (Steam or Epic) and Xbox Series X|S players can dive together in the same session.
Solo ↔ co-op conversion
You are not locked into a choice at world creation. A solo backup can be converted into a multiplayer session at any time, so a single-player save can become a shared one when friends are available — and the world keeps going.
Shared progression
The party shares the things that matter for cooperative play:
- Inventories and storage are shared across the party.
- Data Bank entries are shared — discoveries propagate.
- Crafting recipes / blueprints are shared: one player scanning a fragment unlocks the blueprint for everyone in the group.
This design removes the classic co-op survival friction of every player having to independently re-grind the same tech tree, and makes splitting up to scan different wrecks a genuinely efficient strategy.