Last updated: 13 July 2026

Subnautica 2 Co-op Guide — Play Multiplayer With Friends

Subnautica 2 was built from the ground up to support co-op play for up to four players — a first for the series. Whether you want a friend to share the early terror of an alien ocean or a full team to build an elaborate deep-sea base together, the multiplayer system is designed to feel seamless. This guide explains exactly how to start and join sessions, what players share, and the strategies that make co-op feel like a feature rather than a complication.

01Starting a Co-op Session

Co-op in Subnautica 2 is hosted by one player — the session host. The host's save file is the authoritative world state; all other players connect to it. When the host exits, the session ends for everyone, and progress is saved to the host's file.

How to start or join a session:

• Host: from the main menu, select New Game or Continue, then choose Multiplayer Mode before loading. This starts the session and makes it joinable by friends via Steam.
• Join via invite: the host can invite friends directly through Steam's overlay (Shift+Tab → Friends → Invite). Invited players get a Steam notification and can join with one click.
• Join via friend list: if the host's session is set to Friends-only, any Steam friend can join by right-clicking the host's name in their Steam friends list and selecting Join Game.
• Session privacy: three options — Friends Only (recommended), Invite Only (no one can join without a direct invite), and Private (no multiplayer).

You cannot convert an existing single-player save to a co-op save after the fact in the initial Early Access release — if you want to play co-op, select multiplayer mode before your first session. Check the current patch notes if this limitation has been updated.

02What's Shared Between Players

Understanding what is shared and what is individual prevents frustrating miscommunication in a co-op session.

Shared between all players:

• World state — all resources, creatures, biome changes, and wrecks are in the same world. If one player breaks a Limestone Outcrop, it's gone for everyone.
• Base and all modules — any player with a Habitat Builder can add or remove modules from a shared base. Coordinate before building.
• Fabricator queues — all players share access to any Fabricator in a base. Two players queuing crafts simultaneously works, but material costs are pulled from the shared pool.
• Storage lockers — all lockers in a base are accessible to all players. Set up a convention (e.g. locker labels or designate which player manages which resource type).
• PDA story progress — major narrative events and signals are shared; completing a story trigger for one player updates it for all.

Individual per player:

• Personal inventory — each player has their own inventory and equipment slots.
• Scanner data — scanning a blueprint or creature updates only the scanner of the player who scanned it. Everyone needs to scan key tech themselves.
• Oxygen and hunger/thirst bars — fully individual. One player's air running out doesn't affect others.
• Health — individual. A player who drowns or dies at a creature respawns at the base or escape pod with a resource penalty.

03Best Co-op Role Division

Co-op is most efficient when players divide responsibilities rather than all doing the same tasks. Here's a division that works well for a two-to-four player group:

• Builder (1 player) — focuses on base construction, hull integrity management, and setting up power systems. This player reads the base stats and calls when reinforcement is needed before others add new modules.
• Resource farmer (1–2 players) — dives for materials and fills shared storage. Communicates which resources are low and handles Scanner Room operations.
• Explorer (1 player) — scouts new biomes, scans creatures and flora, and identifies where the next resource or story objective is. This player takes the most risk and benefits most from the Stasis Rifle and Repulsion Cannon.
• With 4 players: add a dedicated Vehicle operator who manages Seamoths and other underwater vehicles, handles Moonpool charging, and provides transport for long-distance resource runs.

These roles aren't mandatory — the game doesn't enforce them — but having one player aware of hull integrity at all times prevents the most common co-op disaster: a well-meaning teammate adding three windows to a base that's already at +1 integrity.

04Co-op Survival Tips

A few practical habits that make co-op sessions smoother:

• Synchronise your scan priorities. Each player needs to scan blueprints individually to craft them. In the first hour, split up in the starting biome — one player scans the northern section, another the south — then meet to compare what you've found.
• Set a shared base chest. Designate one storage locker in your base as a 'drop-off' for all raw materials. Everyone deposits into it; the builder or crafter pulls from it. This prevents two players both mining Titanium while a third is waiting for Copper.
• Call your dives. Before going deep, tell your team so someone can be at the base as a 'home base anchor' — a player who stays shallow and can respond if a diver needs a quick craft or emergency supplies.
• Don't separate indefinitely. If one player goes deep alone, they face the same oxygen and creature risks as solo play. The advantage of co-op is support — stay close enough that a distress call is actionable.
• Vote before major changes. Removing a module from a base, abandoning an outpost, or using rare materials all affect everyone. A quick chat before acting saves friction later.

05Performance and Technical Notes

As an Early Access game, co-op performance in Subnautica 2 may vary with update versions. A few things worth knowing:

• The host's machine determines server performance. If the host has a slower PC or poor internet connection, all players may experience higher latency and stuttering. A player with a stronger machine and stable connection should usually host.
• Save frequency: the game autosaves on the host's file at regular intervals. Non-host players do not have their own save — if the host exits unexpectedly, all unsaved progress is lost. Hosts should save manually after major milestones.
• Re-joining mid-session: players who disconnect can rejoin an active session from the Steam friends list or a new invite, appearing at the base or their last position.
• Version matching: all players must be on the same game version to connect. If one player is on a newer patch, Steam should auto-update everyone when they launch.
• Shiver Leviathan (fixed in update 1.1): a bug in earlier EA builds caused the Shiver Leviathan to not attack non-host players, making it effectively harmless to guests while threatening only the host. This was corrected in update 1.1 'Adaptive Measures' — the Shiver Leviathan now attacks all players in a session equally.

Check the official Subnautica 2 patch notes and community forums for any co-op specific bugs or performance updates relevant to the current version — Early Access updates can change this significantly between patches.