The heat barrier is an environmental gate in Subnautica 2. It is an 80 degree Celsius wall that blocks the player from pushing further into the hottest parts of the world until they gain the Heat Tolerance Adaptation. Rather than a fifth survival meter, temperature in Subnautica 2 is handled as a hazard tied to specific zones, and the heat barrier is the hard ceiling of that hazard.
Escalating Heat in Hot Zones
Heat in Subnautica 2 only matters inside hot zones. Across roughly 30 to 80 degrees Celsius, the heat in these areas deals escalating damage to the player's Health, scaling up the hotter the water becomes. Cooler, temperate biomes carry no heat penalty, so the danger is local: the player only has to manage temperature when approaching geothermal or superheated water, not during ordinary diving.
Because the damage climbs with temperature, an unmodified player can dip into the cooler edges of a hot zone but takes increasingly heavy damage the deeper in they go. At the top of the range, around 80 degrees Celsius, the heat becomes a wall that cannot be crossed by an unprotected diver at all.
Temperature | Effect on the Player |
|---|---|
Below about 30 degrees Celsius | No heat damage; ordinary diving in temperate water. |
About 30 to 80 degrees Celsius | Escalating heat damage to Health, increasing with temperature. |
At about 80 degrees Celsius (the heat barrier) | Progress is blocked entirely until the Heat Tolerance Adaptation is gained. |
Passing the Barrier With Heat Tolerance
The only way past the heat barrier in the current Early Access build is the Heat Tolerance Adaptation, a permanent DNA upgrade. Like other Adaptations, it is drawn from the colored bulb of an Angel Comb growth; the bulb is consumed on use and the upgrade enters the player's genome permanently. Once Heat Tolerance is in place, the player can cross the 80 degree wall and survive the superheated water beyond it.
This makes the heat barrier a classic progression gate. It is not a puzzle to solve in the moment with consumables; it is a hard requirement that the player must come back to once they have earned the right Adaptation, which turns gaining Heat Tolerance into a noticeable turning point in a run.
What the Barrier Gates
Crossing the heat barrier opens access to areas that sit behind the superheated water. Two confirmed locations gated this way are the Graveyard sub-area and the Tadpole Pens. Until Heat Tolerance is gained, both remain out of reach because the heat alone will turn the player back.
Clearing the barrier is part of the broader push deeper into the world. As successive gates open, the player can work toward later regions of Proteus, such as Karakorum. The exact placement of every heat-gated area relative to other gates is best confirmed in the current build, but the role of the barrier itself is consistent: it walls off the hottest content until the player adapts.
Temperature Is Not a Fifth Meter
It is worth restating that the heat barrier and hot-zone damage are the whole of how temperature works in Subnautica 2. The game tracks four standing survival stats, Oxygen, Health, Hunger, and Thirst, and there is no separate always-on temperature gauge. Heat is purely an environmental hazard that activates inside hot zones and culminates in the barrier, so the player never has to watch a body-temperature bar during normal play.
See Also
Adaptations, including Heat Tolerance, the upgrade that opens the barrier.
Angel Comb, the source of Heat Tolerance.
Survival Mechanics, for the four standing survival stats.