Subnautica: Below Zero Walkthrough — Start to Endgame

Subnautica: Below Zero is the standalone follow-up to Subnautica, set in an arctic region of planet 4546B. You play as Robin Ayou investigating her sister's death at an Alterra research station while an alien entity named Al-An shares your mind. The game adds significant land-based exploration across frozen tundra alongside the underwater gameplay, plus the Seatruck — a modular submarine where you attach different functional modules (storage, fabricator, aquarium, sleeper) to create a custom mobile base. Below Zero is smaller and more focused than the original, with a tighter story and less open exploration.

This walkthrough takes you from your first session to endgame content. Each phase has specific goals, priorities, and milestones. Follow this path to avoid common traps that stall most players.

Quick Progression Summary

Phase 1: Getting Started — Twisty Bridges

The starting biome with winding coral bridges and abundant basic resources. Safe and well-lit with minimal predator threats. Contains early blueprint fragments and the initial story triggers. Build your first base here.

Level/Difficulty: 0-100m depth Key Rewards: Basic resources, early blueprints, Seatruck fragments, safe base location

What to Do in Twisty Bridges

1. Learn Seatruck modules. The Seatruck is a modular vehicle where each module attaches behind the cabin. Spend your first session getting comfortable with this.
2. Pick Base Builder as your starting build. It's the most forgiving option.
3. Build the Seatruck before anything else — it provides safe transport, oxygen, and storage. The base Seatruck (no modules) is fast and maneuverable enough for early exploration.
4. Acquire your first equipment upgrade — Seatruck Perimeter Defense or whatever's available.
5. Clear all main content before moving on.

Phase 1 Checklist

• Understand Seatruck modules fundamentals
• Base Builder selected and functional
• Twisty Bridges main content cleared
• Ready for Lilypads

Phase 2: Early Game — Lilypads

A mid-depth biome with massive lily pad structures and the Lilypad Islands on the surface. Contains Seatruck fragments and moderate-danger predators. The Ventgarden creature inhabits a massive cave system here.

Level/Difficulty: 100-300m depth Key Rewards: Seatruck modules, Magnetite, Ventgarden encounter

What to Do in Lilypads

1. Work on cold resistance. Land exploration in Below Zero requires managing body temperature. This system becomes critical from here on.
2. Farm for Seatruck Perimeter Defense if you haven't already. It's the key upgrade for this phase.
3. Detach Seatruck modules before entering dangerous areas. The base cabin alone is much faster than the full modular train. Reattach modules at your base.
4. Complete all objectives before pushing to Crystal Caves.
5. Consider whether Deep Explorer might suit your playstyle better than Base Builder.

Phase 2 Checklist

• cold resistance integrated into gameplay
• Seatruck Perimeter Defense acquired
• Lilypads fully cleared
• Ready for Crystal Caves

Phase 3: Mid Game — Crystal Caves

A deep biome with bioluminescent crystals and dangerous fauna. Contains rare resources (Ion Cubes, Nickel Ore) needed for advanced crafting. The Crystal Caves connect to the Fabricator Caverns and deeper story locations.

Level/Difficulty: 300-600m depth Key Rewards: Ion Cubes, Nickel Ore, deep base resources, story progression

What to Do in Crystal Caves

1. Master alien research. Al-An (an alien stored in your brain) guides you to find components for building him a new body. This unlocks a new layer of gameplay.
2. Start working toward Survival Knife. It's the best equipment and becomes accessible around now.
3. Thermal Plants placed near underwater heat vents generate unlimited free power. Build your main base near a vent cluster for permanent energy.
4. This area is the main skill check. If you can clear it, you're ready for late game.
5. Start investing in base building for the tactical depth you'll need going forward.

Phase 3 Checklist

• alien research mastered
• Survival Knife acquired or in progress
• Crystal Caves fully cleared
• Ready for Glacial Basin

Phase 4: Late Game — Glacial Basin

A frozen surface area with ice caves, Snowstalkers (land predators), and the Phi Robotics Lab. Requires cold-resistance gear. Contains Al-An story progression and the Snowfox hoverbike blueprints. The weather system creates dangerous blizzard conditions.

Level/Difficulty: Surface (cold damage) Key Rewards: Snowfox blueprints, Al-An tissues, Phi Robotics story logs

What to Do in Glacial Basin

1. Finalize your build. You should be running Deep Explorer or Base Builder with optimized gear.
2. Survival Knife should be your primary. If you don't have it yet, prioritize getting it.
3. The Spy Pengling is legitimately useful — deploy it near Leviathan territories to scout safe paths without risking your life or vehicle.
4. creature scanning optimization starts here. Small improvements compound into massive advantages.
5. Farm this area for the resources needed to push into Fabricator Caverns.

Phase 4 Checklist

• Build fully optimized
• Survival Knife upgraded to max
• Glacial Basin fully cleared
• Ready for Fabricator Caverns

Phase 5: Endgame — Fabricator Caverns

The deepest biome containing ancient alien fabrication equipment. Al-An's body construction happens here. Contains the most dangerous deep-sea creatures and the most valuable alien technology. This is where the Al-An questline concludes.

Level/Difficulty: 600-1000m depth Key Rewards: Al-An body construction, final alien technology, deepest exploration content

What to Do in Fabricator Caverns

1. Fabricator Caverns tests everything. Come prepared with your best build and gear.
2. Cold damage on land is managed by: staying near heat sources, wearing the cold suit, building fires with the Flare, and using the Snowfox's heated cabin.
3. The endgame loop: run Fabricator Caverns, optimize gear, push harder content.
4. Experiment with Lore Hunter for a fresh take once you've mastered the standard builds.
5. This is where creature scanning mastery separates good players from great ones.

Phase 5 Checklist

• Endgame content on farm
• Best-in-slot gear acquired
• Fabricator Caverns fully cleared
• Ready for challenge content

Common Progression Mistakes

• Not building a Seatruck early — swimming everywhere wastes oxygen and exposes you to predator attacks. The Seatruck is your first major crafting priority.
• Ignoring cold management on land — cold damage adds up quickly. Always carry a Flare and wear the cold suit in the Glacial Basin.
• Attaching too many Seatruck modules — more modules = slower vehicle. Only attach modules you need for the current expedition. Leave others at base.
• Missing Al-An's body parts — his questline runs parallel to the main story. If you don't visit alien facilities, his story stalls. Follow both quest threads simultaneously.
• Building a base in a predator-heavy area — Chelicerates and Shadow Leviathans attack vehicles near your base. Build in calm biomes like Twisty Bridges or Thermal Spires.

Key Tips for Smooth Progression

1. Build the Seatruck before anything else — it provides safe transport, oxygen, and storage. The base Seatruck (no modules) is fast and maneuverable enough for early exploration.
2. Detach Seatruck modules before entering dangerous areas. The base cabin alone is much faster than the full modular train. Reattach modules at your base.
3. Thermal Plants placed near underwater heat vents generate unlimited free power. Build your main base near a vent cluster for permanent energy.
4. The Spy Pengling is legitimately useful — deploy it near Leviathan territories to scout safe paths without risking your life or vehicle.
5. Cold damage on land is managed by: staying near heat sources, wearing the cold suit, building fires with the Flare, and using the Snowfox's heated cabin.

For detailed build optimization, see Subnautica: Below Zero builds. For quick wins, check tips & tricks.