There exist three Game Modes in Barotrauma Multiplayer: Sandbox, Mission, and Campaign.
"A game mode with no specific objectives."
As the description suggests, there are no rules, no Missions, and no rewards in this Game Mode. The crew is free to do whatever they want in a random level seed, either for the purpose of learning the basics of the game or just for fun. The round ends when the crew reaches the end of the level or everyone in the crew has perished.
It is exclusive to Multiplayer.
"The crew must work together to complete a single mission, such as retrieving an alien artifact or killing a creature that's terrorizing nearby outposts."
The players don't receive any rewards for completing the Missions, and the Game Mode is instead a way to quickly get into the action. The round ends when the crew completes the Mission and reaches the end of the level or everyone in the crew has died.
There are four Mission types available to choose from in the lobby, each with a multitude of different objectives:
- Salvage - Salvage Missions mainly require the crew to retrieve a specific important object such as one of the five Artifacts or the captain's Logbook with encrypted data inside a shipwreck.
- Monster - Monster Missions typically include objectives like taking down medium and large Creatures, swarms of Creatures, or destroying a nest of creature eggs in a cave.
- Cargo - Cargo Missions are delivery runs between Europan Outposts. You can deliver things such as building materials to help construct new Outposts, medical supplies, weapon materials, dangerous chemicals, explosive compounds, clown stashes for the Honkmother's syndicate, people who want to relocate to a new outpost, and even infectious parasitic eggs for researchers!
- Combat - Taking on a pirate ship in sub-to-sub combat. There is also a Multiplayer-only mode called Search and Destroy where the Coalition and Renegades participate in submarine battles.
If the host unticks all four Mission types and starts the round, no Mission will initiate, meaning the gameplay will be very much like Sandbox.
"Embark on a journey through the depths of Europa. Travel from location to location, complete missions to earn money for supplies, discover new biomes…"
This is the only Game Mode available in both Singleplayer Campaign and Multiplayer.
Upon choosing this Game Mode in Multiplayer, the host can choose to either start anew or load an old Campaign save. When starting a new Campaign, a Submarine that isn't an outdated modded Sub must be chosen and once the game starts, it cannot be changed in the server lobby anymore. All purchasable Submarines, which are available in the Shipyard, are selected by default. However, the host has the option to deselect whichever Subs they want to leave out of the game. Lastly, the save name must be entered in order to start the game.
The crew will then be taken into an explorable Colony and may begin their journey from there. The gameplay is similar to Singleplayer Campaign.
Traitors is a special function in Multiplayer. When enabled, depending on the Traitors setting, random players will be selected as the Traitors. They will be tasked with various objectives a few minutes after the game starts. Usually, Traitors start with searching for a specific item in a vent, locker or a supply cabinet. Once the item is obtained, the Traitors will be given further instructions. These instructions could be to sabotage specific installations, assassinate a specific crew member, and more.