Barotrauma

Great game, hardest part is getting your friends to play it.
Edit after 400 hours: You don't get your friends to play this, you make friends on public servers.

Here is my most recent experience in 10 simple steps.
Step 1. Listen to the captain get mauled by crawlers
Step 2. Try to repair the sub
Step 3. Watch as the Engineer becomes husked
Step 4. Kill Engineer
Step 5. Struggle to operate the sub as one man due to mod that makes the reactor go critical easier
Step. 6. Almost make it to an outpost (practically the entire sub is destroyed and the sub is only running on backup batteries)
Step 7. Get 5 meters away from docking and run out of power whilst sinking to the abyss because another crawler busted its way into the sub
Step 8. Repair the sub again only to find that the sub is now over 550 meters away from any outpost
step 9. Set the sub to auto-pilot and man the reactor so it doesn't go critical
Step 10. The host's game crashed and my efforts were futile (I was almost there)
20/10 would suffer from barotrauma numerous times again.

very fun game to play with a large group of friends and roleplay
until they beat the game without you because you arent on for 1 day out of the 20 you guys played.

If you've never experienced running a nuclear reactor, going off to go fix something when the captain asks, coming back to the nuclear reactor, getting hit in the jugular by a 10 inch spike fired from outside the ship by nightmares beyond your comprehension, slowly bleeding out while the medic is trying to put out all the fires (plot twist they only exist in his head), and watch as the ship clown enters the reactor room, alarms start blaring, and the nuclear reactor detonates, instantly vaporizing the entire ship (and the contingent of immortal zombies lurking outside it). Then play this game, that'll happen

Barotrauma is an ambitious game. That's the most honest way to describe it. It wants to do a lot. And as a result, many of its parts are undercooked. BUT...
The premise of the game and its core idea are wonderful. You are taking a long journey with your friends through the underwater hell that is Europa, piloting and maintaining a shoddy submarine, purchased at a suspiciously low price. You watch Europa's resource-starved human society crumble as a result of a natural disaster, and try to make the best of this terrible situation.
The gameplay is what you make of it. You can settle into a relatively comfortable role on a submarine, doing the intended job of your class. Or you can do a bit of everything - maintaining devices, handling navigation, manning the turrets to keep aggressive creatures away, going outside to mine and salvage materials... The class you choose doesn't limit the selection of jobs you can be competent at. And everything gets better with teamwork.
Barotrauma's developers are working tirelessly to improve the game. I've been here for a couple of years, playing the game actively and aiding the devs in its development, alongside other community regulars. In that time Barotrauma has changed a lot, with a bunch of its features getting more fleshed out. Each update bringing much needed improvements, based on the team's own vision and community feedback.
Steam Workshop support is part of the game's appeal as well. There is a lot of custom content out there. Some balanced, some not. With mods and a wide selection of in-game settings, you can craft whatever experience you want for your campaign. Though I do recommend doing a vanilla run first, all the modded stuff can keep things fresh in the future playthroughs.
Singleplayer mode is available and is actually pretty okay, but I'd really recommend playing the game with actual people. Barotrauma is a prime environment for fun social interactions. The game goes on sale relatively often, so keep an eye out for that and pick it up with your friend group. The base price is steep (thanks, Daedalic), but getting Barotrauma with a 50% discount is a good deal.

I own a railgun for submarine defense, since that's what the founding Europans intended. Four clowns break into my sub. "What the Jove?" As I grab my Renegade's hat and Model 6 Impierta Railgun. Blow a crawler-sized hole through the first clown, he's dead on the spot. Draw my handcannon on the second clown, miss him entirely because I don't have enough weapons skill and nails my crewmate's Petraptor. I have to resort to the detonator mounted at the top of the stairs loaded with C-4, "Tally ho lads!" the explosion shreds two clowns in the blast, the sound and extra shrapnel set off nearby Molochs. Fix boarding axe and charge the last terrified buffoonist. He bleeds out waiting on the medical doctor to arrive since bleeding wounds are impossible to heal with morphine. Just as the founding Europans intended.

this is by far my favorite game ever. Barotrauma looks simple, but there's so much you can do. Take the reactor for example. It isn't just a thing that you put a fuel rod in and everything has power, it sends its power through actual wires that can be rerouted, added to new things, or just fully removed and splits it up through actual junction boxes that can break. If you have the manpower you can manually control the reactor, changing how much heat it produces and how much power it makes, making it (ideally) more efficient and easing out the power fluxuations that turn off lights or overvolt devices. (or you can turn fission all the way up and turbine all the way down and blow it up, but you didn't hear that from me.) wires dont just transfer power btw. you can set up systems that range from showing a display of how much fuel is in the reactor to a lever that makes all the light strobe RGB. that's all just wiring. there's a medical system, ship upgrades, crafting and deconstructing, pulling off an away mission without a hitch is an artform, you get the point. or you can just say "fuck all that" and be a clown, get clown powers and become powerful enough to kill god. there's so much other things that can happen, too. this game can go from 0-100 in an instant. if the game looks fun to you, get it. if it dosen't look fun to you, get it anyway. there's plenty of mods that can fix any problem you could possibly have with the game. hell, there's a mod that adds an incredibly realistic medical system. that's one of the more popular ones, along with a mod that turns everyone into busty anime women. in short, game pog.