Stepping outside the safe shallows on Planet Proteus is one of the most exciting and fatal things you can do in Subnautica 2. Heat, pressure, hostile fauna, and dwindling oxygen all compound into a single, unforgiving message: you are not ready.
This guide explains exactly how dangerous zones work, what protection you actually need to survive them, and what to bring before you attempt the run.
Subnautica 2 entered Early Access on May 14, 2026. Heat Tolerance requirements and resource locations may change with future updates. All data in this guide reflects the Early Access launch build as of May 19, 2026.
1. How Heat Zones Work
Rising Water Temperature Warning
Subnautica 2 uses environmental hazards as progression gates. The most dangerous of these in the current Early Access build is heat. On Proteus, heat is the primary environmental hazard, and you need the Heat Tolerance Adaptation before you can explore those biomes safely.
When you approach a high-temperature biome, the game warns you through several immediate indicators:
- PDA Warning: Your suit’s AI triggers an audible temperature alert.
- HUD Indicators: A red arc appears on your screen, pointing directly toward the heat source.
- Health Drain: The longer you stay exposed to the heat, the faster your health drops.
Heat Tolerance Adaptation
The Adaptation system is how protection works here. You gain permanent biological upgrades by interacting with large alien plant structures called Angel Combs.
The Heat Tolerance Adaptation rewrites your DNA to survive these biomes, altering your survival thresholds significantly:
- 30 to 70 Degrees: Without the adaptation, you take rapid, continuous damage in this range.
- Above 80 Degrees: Without the adaptation, the heat damage becomes fatal within seconds.
- 100-Degree Limit: Even with Heat Tolerance active, your maximum safe threshold is 100 degrees Celsius.
- Active Vents: Specific areas directly over active thermal vents exceed this 100-degree limit and will still burn you.
2. How to Unlock Heat Tolerance
Heat Tolerance is the third Adaptation in the game, coming after Pressure Tolerance and Digestion. Unlike the first two, Heat Tolerance requires you to craft a specific tool and clear a multi-stage infection inside a dangerous cave system.
Having these items prepared makes the cave significantly safer and sets you up for the follow-up hot zone run.
- Sonic Resonator (Important): This tool is mandatory to destroy Bloom Cankers and begin the process.
- Recommended: Standard Air Tank (or multiple Air Bladders), First Aid Kit, Distraction Flares, and a Beacon.
Getting the Sonic Resonator
Sonic Resonator Blueprint
The Sonic Resonator is required because it destroys the Bloom Cankers, sealing the Angel Comb. Scan the blueprint fragments at the Old Habitat, roughly 350 meters north of your Lifepod, then craft the tool before attempting the cave run.
Crafting the tool requires metal ingots, so check the Scanner Station for resource locations.
Once you have the Resonator, make sure you also equip a Standard Air Tank. The cave system hiding the Angel Comb is deep and dark. If you lack the Air Tank, bring at least two or three Air Bladders and Distraction Flares.
Clearing the Angel Comb
Angel Comb Structure
- From your Lifepod, swim about 200 meters northwest, then look down for the trench sealed by Bloom Biofilm.
- Fire the Sonic Resonator to open the entrance and enter the cave.
- In the main chamber, follow the large tendrils and destroy the Bloom Cankers attached to the tunnels.
- Follow the PDA prompt north to the second infection site and destroy every Bloom Canker there. Use a flare if Nibbler Mangoes patrol the area.
- Return to the central Angel Comb and destroy the four new Bloom Biofilm blossoms while avoiding or repelling the infected Marrowbreach.
- Interact with the glowing pink core to permanently unlock Heat Tolerance.
Unlocking Heat Tolerance is a key progression gate. It allows safe entry into the hot biome where Gold and other important mid-game resources are located, and opens the path toward the Tadpole and further story objectives.
3. What to Bring Before Entering Hot Zones
The Tadpole Submarine
Unlocking Heat Tolerance is not the same as being ready to explore hot zones safely. The high-temperature biomes on Proteus hold the best mid-game resources, but rushing in unprepared is a quick way to die.
Always pack the following items before your first serious run into the heat:
- Standard Air Tank: Hot-zone caves run deep, so you need extra oxygen capacity for longer resource runs.
- Distraction Flares: Hostile creatures patrol heat zone caves; flares buy you the seconds needed to harvest nodes without taking damage.
- First Aid Kit: Thermal vents in the deepest parts of hot biomes still exceed your 100-degree threshold and deal damage. Carry at least one med kit.
- Food and Water: Bring supplies before long hot-zone dives; running out of hydration mid-run is an avoidable way to die.
- Beacon: Place a beacon at the entry point. Navigation inside hot-zone cave systems is difficult, and a beacon ensures you can find your way out.
- Tadpole Submarine: This vehicle extends your reach, provides a refillable oxygen source, and offers critical storage space for everything you collect.
4. Resources Inside Hot Zones
Hot zones are relevant for progression because two of the most important mid-game crafting materials, Gold and Sulfur, are locked exclusively behind heat zone entry.
Neither resource appears in the cooler starter biomes, and both are required for advanced tools like the Repair Tool and Thermal Plant.
- Gold: Found in heat zone ore deposits; primarily used for electronics and advanced tools like the Advanced Wiring Kit.
- Sulfur: Harvested from heat zone floor nodes; critical for crafting explosives, chemicals, and the Repair Tool.
- Wreck Fragments: Scannable objects in heat biomes provide blueprint progression that safer starting zones cannot offer.
If you are trying to unlock the Tadpole Depot and progress further into the story, the hot biome run is entirely mandatory.
5. Common Heat Zone Mistakes to Avoid
Most deaths in Subnautica 2‘s dangerous zones stem from the same set of errors. Understanding them before you go in is faster than learning them after respawning.
- Entering Without Heat Tolerance: If your PDA triggers a temperature warning, stop immediately. The damage scales too fast to survive on raw health alone.
- Treating the Adaptation as Full Immunity: Heat Tolerance only protects you up to 100 degrees Celsius. Active thermal vents still exceed that limit and deal damage.
- Going In on Base Lung Capacity: The Angel Comb cave system and hot biomes require more oxygen than your default tank provides.
- Not Marking the Cave Entrance: Place a beacon at the mouth before entering. Without one, it is easy to get turned around and run out of oxygen on the way back.
- Ignoring Creature Audio: The game communicates the presence of creatures through sound before visual contact. If you hear something large, back up and assess.
- Overpacking Inventory: Going in full of resources from earlier exploration leaves no room for Gold and Sulfur. Clear your inventory before every run.
- Skipping the Sonic Resonator: The Angel Comb entrance is sealed by Bloom Biofilm. Without the Sonic Resonator, you cannot proceed, and the trip is wasted.
