FULL METAL COFFIN

A submarine built for four, and for real teamwork

FULL METAL COFFIN puts up to four players inside a fully explorable 3D submarine and sends them into flooded caverns beneath Antarctica, tasking the crew with loading torpedoes, tracking threats on sonar, and keeping the vessel intact under fire. One detailed reviewer captured the design intent well, describing it as a game that "builds its identity around teamwork, tactical preparation, and the pressure of operating a complicated vessel in hostile underwater territory," putting players "inside the machine itself" rather than presenting submarine combat from a detached strategic remove. That framing lands well with reviewers who played it as intended: one called the combat "adrenaline inducing" while staying "very balanced. Complex, but not too much," and another specifically praised how the game "shines with teamwork" once played with a coordinated crew rather than solo.

A genuinely distinctive sonar hook

The specific mechanical hook reviewers single out most is the sonar system, with one comparing its scanning style to "Scanner Sombre" crossed with the tense crew-management pressure of "Barotrauma" — two well-regarded reference points that signal real thought went into making detection and threat-tracking an active, skill-based part of play rather than a passive radar blip. Multiple reviewers also flagged a specific mechanical wrinkle worth knowing before jumping in: the sonar panel's scanning arc can be expanded or shrunk, but the game gives no in-game indication of this, with one group only discovering the option by checking the controls menu directly.

A genuinely tiny amount of content

The most consistent, corroborated complaint across the review pool concerns raw content volume. One reviewer laid out exactly what's on offer at launch: "1 Enemy Type - 1 Submarine Type to control - 3 Wave Survival Missions - 3 Torpedo Types," noting bluntly that "it's more of a demo at the moment," and expressing surprise the game wasn't released as Early Access given how sparse that is. That assessment was echoed independently by other reviewers: one described finishing "the 3 missions" solo in about an hour each, and another, while still recommending the game, called having "only 3 missions" genuinely "heartbreaking" given how much they enjoyed what was there. For context, most groups report finishing all available content in roughly two hours, which at $4.99 is a defensible value proposition for a short co-op session, but a real limitation for anyone hoping for a longer-term co-op staple.

Crashes and performance problems on some setups

A second, more serious cluster of complaints concerns stability and optimization. One negative review was blunt about the mismatch between the "simulator" label and the actual experience, calling it "very arcadey and not a 'simulator'" with "quite a lot of bugs," and reporting performance so poor that an RTX 4060 struggled to hold 30 FPS, attributing the problem specifically to "negligence in optimizing lighting." Two other negative reviews reported outright inability to connect or play at all: one described the game refusing to let them and a friend connect, with "constant crashing," while another reported repeated crashes and a black-screen issue that persisted even after switching rendering APIs. These aren't universal complaints — most of the positive review pool reports a smooth experience, including one reviewer who called the overall quality "insane" for a newly released small game — but the crash and performance reports are specific and detailed enough to flag clearly for anyone on less common hardware configurations.

A fast-moving solo developer

Context matters here: the game's own launch-week announcement confirms this is a solo developer's first-ever release, and the post-launch patch cadence backs up a real commitment to fixing exactly the problems reviewers raised. Two stability patches shipped within roughly a month of launch, fixing an out-of-bounds exploit near the crafting terminals, correcting faulty enemy AI networking calls, and adding several requested quality-of-life settings including a new helm control mode. The developer's own roadmap post, written directly in response to the community's "warm reception," promises two to three more stability passes alongside additional content — a genuinely encouraging signal that the thin mission count and rougher technical edges are being actively worked rather than left as-is.

A cheaper, tighter alternative to the genre's biggest name

Co-op submarine sims live largely in the shadow of Barotrauma, which has spent years building out an enormous, systemically deep simulation of crewed underwater survival. FULL METAL COFFIN doesn't attempt to compete on that scale, and reviewers seem to understand and largely accept that trade-off: its pitch is a tighter, more combat-focused wave-defense loop that a group can pick up and finish in a single sitting, at roughly a quarter of Barotrauma's asking price. That's a genuinely different niche within the same broad genre rather than a direct competitor, and for groups who find Barotrauma's scope intimidating or don't have the multi-session time commitment it demands, FULL METAL COFFIN's compact scope is arguably a feature rather than a limitation — provided buyers go in understanding just how compact "compact" currently means, at three missions and roughly two hours of total content.

Verdict

FULL METAL COFFIN delivers real, adrenaline-inducing co-op tension built around a genuinely clever sonar system and well-balanced wave combat, and does so with a level of polish that's impressive for a solo developer's first release. Its problems are concrete and specific rather than vague: barely two hours of mission content at launch, and reported crashes and performance issues on some hardware that go beyond isolated one-off complaints. Worth buying for co-op groups who want a short, tense, well-priced submarine session and are willing to accept its current thinness as a starting point rather than a finished package; players who need a longer-term co-op staple, or who are on less common hardware, should watch the developer's promised follow-up patches before diving in.