How to Install Barotrauma and Join a Server

The submarine is flooding, the lights have gone out, and the person who was supposed to be fixing the reactor is currently on fire in the airlock. Nobody did anything wrong on purpose. That is Barotrauma working correctly.

It is a side-on, 2D submarine simulator set under the ice of Europa, and it is one of the very few co-operative games where the enemy is mostly your own crew's competence. There are monsters outside. They are the second problem.

Listings for it collect on the Barotrauma hub, and this guide covers getting in, picking a job and surviving your first hour without being ejected through a hull breach you caused.

What you are actually crewing

The submarine is a cross-section. You see every room at once, every door, every pipe, and everyone in it. That single design decision is why the game is funny and why it is stressful — you can watch a disaster develop three rooms away and be unable to reach it.

Everything on the boat is simulated rather than abstracted. The reactor produces power, the power runs through junction boxes to the devices that need it, and if the junction box in a flooded room shorts out then the lights, the doors and the weapons stop working in a pattern that makes sense afterwards and no sense at the time. Water enters through holes. Holes are made by monsters, by collisions, and by crewmates with mining tools.

Oxygen runs out. Fires spread and consume it faster. Doors can be welded shut, which is sometimes a repair and sometimes a murder.

The jobs, and what each one is for

You pick a job before the round starts. They are not cosmetic.

Captain drives and commands. Steering a submarine is genuinely a skill — the boat has momentum, the caves are tight, and hitting a wall at speed damages everything on that side of the hull. A captain who cannot navigate quietly is a captain who arrives at the destination with no crew.

Engineer owns the reactor and the electrical grid. This is the highest-leverage job on the boat. Get the reactor's output matched to the load and everything works; get it wrong and you either brown out the boat or produce a meltdown, and the second one ends the round for everybody.

Mechanic repairs the physical boat. Welding hull breaches from the inside while water rises, fixing pumps, keeping the ballast working. Unglamorous and the reason anyone survives.

Medical Doctor keeps people alive. Barotrauma's medicine models specific afflictions rather than a health bar, and treating the wrong one — or the right one with too much of the drug — kills the patient. A doctor who has read the labels is worth more than an extra gun.

Security Officer handles what gets inside, and occasionally what is already inside.

Assistant is the job with no responsibilities and therefore the job where new players learn the boat. Take it first. Follow somebody around. Nobody minds an assistant asking questions and everybody minds an engineer who did not.

Getting it

Barotrauma is a paid game on Steam. Buy it, install it from your Library. The download is modest and the hardware requirements are low — this is a 2D game, and what taxes a machine is a large crew and a lot of simulated water rather than anything on screen.

If Steam itself is new, our guide to installing Steam covers the account and its security first.

Do the tutorials. This is not a game where the tutorials are optional politeness — the reactor, the medical system and the wiring are all genuinely opaque, and half an hour offline is the difference between contributing and being the reason the round ended.

Finding a server

Multiplayer is behind the main menu. The game keeps its own server browser with filters, and you join from inside it rather than from a console or an external launcher.

The list gives you a few things worth reading before you click:

• Whether the campaign is running. A campaign server has a persistent boat, persistent money and a crew who have been building towards something. Dropping into that as a stranger is different from joining a one-off mission.
• The mod list. Servers running workshop content will want your client to match, and the game handles fetching what you are missing. Expect that first join to take longer than the second.
• Traitor settings. Some servers run with traitors enabled, where one crew member has been given a secret objective. Others do not. It changes the social temperature of the whole round.
• Player count against slots. A four-person boat and a sixteen-person boat are different games. Our note on how many slots a game server should have explains why the number is a design decision rather than a maximum.

The browser also accepts an address typed in directly, which is how you join a friend's box or a community server that is not advertising itself publicly. Take the whole address including its port — hosts running several games on one machine move most of them off the default, and an address without a port is the usual reason a join silently fails.

Listings gather on the Barotrauma server list, where each entry is queried directly rather than taking a server's word for its own population.

Your first round, in order

1. Take Assistant. Genuinely. Do not take Engineer because it sounds interesting.
2. Find the reactor and the engineer. Learn where the room is. You will be sent there in an emergency by somebody who assumes you know.
3. Pick up a diving suit and an oxygen tank early. The moment you need one, the locker is underwater.
4. Learn the welding tool. Sealing a breach is the single most useful thing an untrained crew member does, and it takes about a minute to understand.
5. Say what you are doing. Out loud, on voice. "Flooding in the engine room" is worth more than any amount of competent silence.

That last one is the whole game. A crew of six good players who do not talk loses to a crew of six mediocre players who do, every time.

The things that will kill you

The reactor. Left unattended it does not simply idle. A boat drawing more power than the reactor is producing browns out; a reactor pushed past its limits melts down and irradiates everyone. If you are not the engineer, do not touch it.

Your own crew's weapons. Firearms indoors, in a 2D cross-section, with everyone crammed into a corridor. The friendly fire is not always an accident, but most of it is.

Medicine. Barotrauma's drugs have overdose thresholds and interactions. Injecting somebody repeatedly because they are still hurt is a common and fatal instinct.

Welding a door shut on yourself. Extremely common. The tool does not ask whether you are on the correct side.

Husks. There is an infection in this game, and a crewmate who has been bitten and says nothing becomes a problem later. Doctors should be checking. Everyone should be reporting.

Going outside. The water is where the monsters live. A diving suit and a job to do out there is fine. Curiosity is not.

Traitors, on the servers that run them

Some servers enable a mode where one crew member is handed a private objective that the rest of the boat would object to.

What makes it work is that Barotrauma kills people constantly without any help. A traitor does not need to be clever. They need to be somewhere plausible when the thing they arranged goes wrong, and the boat's ordinary background of fires, floods and mistaken welding gives them all the cover they will ever need.

What makes it difficult is that accusing the wrong person costs the crew a working engineer. Servers that run traitors tend to have strong opinions about how far the accusations are allowed to go, and those opinions are in the rules.

Check the setting before you join. Playing a co-operative round on a server where somebody is quietly sabotaging the reactor is a different evening from the one you signed up for.

Campaign servers and why people stay on them

The one-off mission is the demo. The campaign is the game.

In campaign, the boat persists between rounds. Damage carries over, money accumulates, upgrades get bought, and the crew develops opinions about which submarine to spend the budget on. A round that goes badly is not reset — you limp back with half a hull and spend the next one paying for it.

That persistence is what turns a Barotrauma server into a community rather than a lobby. The regulars know the boat's quirks. They know which junction box always shorts. They have a running argument about the reactor.

It also means joining an established campaign server has social weight. Read whatever rules the server publishes, and if it has an application process, that is not gatekeeping for its own sake — our piece on running a whitelist people actually apply to explains why persistent-world servers end up needing one.

Mods, submarines and the editor

Barotrauma ships an editor for building your own submarines, and the workshop is full of them — everything from careful recreations of the stock boats with better wiring to enormous vessels that no crew of six could ever staff.

The rule for joining servers is simple: the server decides. You do not need to subscribe to a collection in advance, and doing so occasionally causes more problems than it solves. Let the server tell your client what it needs.

If you are building, be aware that a submarine which works beautifully in the editor can be miserable to crew, because the editor does not simulate six people trying to get through the same door while the room fills with water. Test with people before you inflict it on strangers.

Hosting for a group

The game will host from inside itself, which is enough for an evening with friends who are all online at once. The limits are the usual two: people outside your network cannot reach your machine unless the router has been set up to allow it, and the moment you quit, the world stops existing.

For a campaign that continues while you are asleep, you want a machine that stays on. Our breakdown of what game server hosting costs covers what that actually runs to, and choosing a region matters here less than in a shooter but still decides whether your European friends can hear you without a delay.

If you like this, the neighbours

Barotrauma's particular trick is systems complex enough that failure is interesting. A few other games do that.

Space Engineers is the same idea in three dimensions and with more building — ships you construct block by block, with power and pressure and the same capacity for a small mistake to vent everybody into space.

Project Zomboid shares the top-down-ish perspective and the commitment to modelling things most games abstract, though the failure there is slower and lonelier.

Valheim and Sons of the Forest are the friendlier end of co-operative survival, where the group's incompetence is survivable and nobody has to understand a fission reactor.

None of them will give you the moment where the lights go out and six people start shouting at once. That one belongs to the submarine.

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JoinGG is a live directory of community game servers. Every listing is queried directly every fifteen minutes, so the player count you see was measured rather than reported by its owner, and each one carries a copyable connect address. Barotrauma servers are listed here, and every game on the site has its own hub. Player counts across every game are on the statistics page.