Subnautica 2 Walkthrough: Main Story Path, Best Biomods & Hidden Discoveries

The main story of Subnautica 2 follows a trail of breadcrumbs left by the original Cicada colonists. You're piecing together what happened during the 25 years between the crash and your creation. Along the way you'll encounter the remnants of the Axum civilization, the degraded Tailings, and the source of the Proteavirus.

This walkthrough covers the critical path. Not every side area. Not every optional blueprint. The things you need to progress the story without getting lost or killed.

Phase One: The Shallows and Cicada Wreckage (Hours 1-5)

NoA starts feeding you coordinates as soon as you repair the radio. Follow them in order. The first few signals point to debris fields from the Cicada's breakup. Each field has data logs and fragment spawns.

The most important early signal is the Cicada's bridge section. It's at about 120 meters east of the starting Shallows. Inside the bridge you'll find the first real story log. It mentions the Proteavirus by name. It mentions a research outpost in the Vine Tangle. It mentions the Axum structures deeper down. This log is the trigger for the next phase.

If you miss this log, the story stalls. NoA won't give you the next set of coordinates. You'll wander around wondering what to do. Don't skip the bridge.

During this phase you should also build your first base, unlock the Propulsion Pack, and start scanning for Biomods. Bioluminescent Vision is your friend. Enhanced Grip Strength speeds up resource gathering for the crafting requirements ahead.

Phase Two: The Vine Tangle and Colonist Outposts (Hours 5-10)

The Vine Tangle is the Kelp Forest equivalent on Proteus. Orange glowing vines. Stalker-like creatures called Vine Reachers. They're aggressive but predictable. They lunge, miss, and pause. Swim past during the pause.

There's a colonist outpost in the Tangle at roughly 180 meters. It's a small modular base built into a rock overhang. Inside you'll find more data logs, a sealed medical bay, and a key item: the first Biomod expansion blueprint. This gives you the ability to craft additional Biomod slots. It requires materials from the Reef Shelf, which is your next destination.

The log in this outpost is dark. It describes the early days of the Proteavirus outbreak. People getting sick. Quarantines failing. The decision to stop printing new colonists. This is where the story's tone shifts from survival to something more unsettling.

By the end of this phase you should have the Tadpole with at least the Scout chassis, two Biomods equipped, and a base with a Scanner Room.

Phase Three: The Reef Shelf and Axum Contact (Hours 10-15)

The Reef Shelf is the first genuinely deep biome. 200 to 350 meters. Wide open spaces. Large passive creatures like the Reef Gliders. Also large aggressive creatures.

The story sends you here because the colonists discovered Axum technology in this biome. There's an alien structure on the shelf. Partially collapsed. Inside is a functioning Axum terminal. Interacting with it triggers a vision sequence. You see the Axum. You see what happened to them. You see the origin of the Bloom.

This is the narrative midpoint. Everything before this was setup. Everything after this is consequences.

The Reef Shelf also has the best resource density in the game. If you need to stockpile for base expansion or Tadpole upgrades, this is the place. Bring the Cargo chassis and Enhanced Grip Strength. One trip should net you enough materials for several hours of crafting.

Phase Four: The Fungal Basin and the Bloom (Hours 15-20)

The Fungal Basin is where the story gets weird. This biome is covered in fungal growths that pulse with green light. The Bloom parasite is everywhere. The Titan is here.

There's a research outpost in the Basin at 450 meters. It's the most intact colonist structure I've found. Multiple rooms. Functioning equipment. Data logs from the head researcher. These logs connect the Proteavirus to the Bloom. They confirm that the Axum were trying to contain something. They failed.

Scanning the Titan in this biome unlocks a unique Biomod: Tissue Regeneration. It slowly heals you over time. Not fast enough to save you in combat. Fast enough that you stop needing medkits for minor damage. This is the best defensive Biomod in the game.

The Basin is also where you'll find your first Ion Cube. It's in a small Axum structure near the Titan. The cube opens the vault deeper down. Don't miss it.

Phase Five: The Trench and the Tailings (Hours 20-30)

The Trench is the deepest accessible biome in the current Early Access build. 400 to 800 meters. Dark. High pressure. Lurkers. The atmosphere shifts from exploration to endurance.

The Tailings live here. They're the degraded descendants of the Axum. Humanoid. Bioluminescent. Hostile if you get close. They guard the entrances to the deepest Axum structures.

This is where the story currently ends in Early Access. You reach a massive Axum facility in the deepest part of the Trench. You learn what the Axum were trying to do. You learn what the Bloom actually is. And then the game tells you that the rest is coming in a future update.

It's an unsatisfying stopping point narratively but the journey to get there is worth it. The Trench is the best designed biome in the game. Claustrophobic. Dangerous. Beautiful in a terrifying way.

What Comes Next

Unknown Worlds has announced that future Early Access updates will add the deeper Void biome, the conclusion to the Axum storyline, and what they're calling the "Final Archive." No dates yet.

For now, reaching the Trench facility is the end of the critical path. Everything after that is exploration for its own sake. The Void is accessible but incomplete. The portal platform is there but inert. The deepest parts of the ocean are waiting.

My recommendation: follow the main path through the Trench facility. Then spend time upgrading everything. Max out your Biomods. Fully upgrade the Tadpole. Explore every corner of the existing biomes. When the next content update drops, you'll be ready.