Subnautica 2 — Biomes & Dangerous Fauna: Every Region and How to Survive It

Tested against: Subnautica 2 early-access build available at the time of writing. Biome names, leviathan patrol paths, and fauna behaviour described here reflect the EA build’s behaviour as understood from public dev updates and the studio’s early-access patch notes. EA values may shift between patches — verify against the in-game PDA and scanner before relying on specific threat patterns.

Subnautica 2’s ocean is layered. Each depth band is its own ecosystem with its own lighting, its own food chain, its own threats. Knowing which biome you’re entering, what’s dangerous there, and how to survive it is the difference between an evening of salvage and an evening of respawns.

This guide walks every biome in EA, top to bottom, and gives you the three things you need: what it looks like, what’s dangerous, what to do about it.

How biomes work in Subnautica 2

The planet’s ocean is a vertical column. As you descend, lighting drops, pressure rises, and the fauna gets more dangerous. There is no horizontal “biome map” — the same stretch of seabed transitions smoothly from one band to the next. The “biomes” below are depth-band labels, not distinct regions.

Rule of thumb: any biome below 200 m requires at least one pressure-resistance gene to enter safely. Any biome below 800 m requires heat immunity and toxin immunity.

Biome 1 — Kelp forest (0–150 m)

The starter biome. Tall, swaying kelp stalks create a curtain effect that limits long-distance vision. Lighting is good during the day, dim at night. Fauna is small and mostly passive.

Visual signature

Sandy seabed, dense kelp stalks rising from the floor, scattered coral outcroppings. Surface light penetrates fully. Bioluminescence appears at night.

Fauna

Species	Behaviour	Threat level
Coral crabs	Passive	None
Glow jellies	Passive drifters	None (don’t touch them)
Water slugs	Cluster near yellow algae	None
Stalker (rare)	Curious, attracted to metal	Low — they steal loose items

What’s dangerous

Almost nothing in the kelp forest is lethal. The biggest threats are:

• Oxygen depletion during extended dives
• Confusion if you wander too far from the lifepod in the dark
• Acid pods that pop if you slash them carelessly (minor splash damage)

How to survive

• Stay near the lifepod in your first session
• Bring 2 emergency bladders
• Mark the lifepod’s position in your PDA’s signal map

Biome 2 — Sparse seafloor (150–400 m)

A wide, mostly empty expanse with low ridges and silver-coral clusters. Lighting drops off noticeably. Visibility is 30–40 m on a clear day.

Visual signature

Open sandy bottom, scattered silver ore outcroppings, occasional cave networks. Light is dim. The water takes on a darker blue tint.

Fauna

Species	Behaviour	Threat level
Stalker	Pack hunters, attracted to metal	Medium — bites drain health
Bone shark	Pack hunters, fast	Medium — chases in groups
Cave crawler	Defensive in caves	Medium — ambush from walls
Reaper-class leviathan	Apex predator	Extreme — one-shot kill

What’s dangerous

The Reaper-class leviathan is the single biggest threat in the entire biome. It’s attracted to lights and movement. It patrols on a roughly 90-second cycle between fixed waypoints.

How to survive

• Lights off. Always.
• Drift silent. Movement creates wake, which creates noise.
• Stay near caves. Use terrain to break line of sight.
• Don’t use the emergency bladder unless you’re sure the leviathan isn’t following.
• If it sees you, swim directly away (not toward caves) — your goal is to break its aggro range, not to lead it to your base.

Common mistake: panicking and surfacing. The leviathan will usually follow you up. Stay deep; leviathans rarely follow players all the way to the surface.

Biome 3 — Jellyshroom plateau (400–800 m)

A bioluminescent wonderland. Giant jellyshroom structures rise from the seafloor like glowing mushrooms. Lighting is provided by the fauna itself, not the surface.

Visual signature

Pitch black in unlit areas; vivid pink, blue, and green glow near any living structure. The water has a slight current that pushes you east-northeast.

Fauna

Species	Behaviour	Threat level
Glowfish	Schools, passive	None
Jellyfish	Drift colonies	Medium — toxin damage on contact
Crabsquid	Electrical, hostile	High — drains oxygen tank
Ghost leviathan	Apex predator	Extreme

What’s dangerous

Two threats here:

• Jellyfish colonies — touching them does toxin damage. The defensive workaround is to hold a light stick in front of you as you swim. Sustained light makes jellies back off.
• Ghost leviathan — patrols the lower edge of the plateau. Same rules as the Reaper: lights off, drift silent, use caves for cover.

How to survive

• Always carry a light stick
• Scan glowfish from a distance (don’t get close)
• Plan your route to avoid the ghost leviathan’s patrol path
• Bring extra oxygen tanks

Biome 4 — Thermal vent & decay zones (800–1,500 m)

The mid-game’s main story arc. Hot thermal vents vent superheated water from the planet’s interior. Decay zones are pockets of alien-killing pathogen.

Visual signature

Dark red water from the iron-rich vents. Glowing orange vent mouths on the seafloor. White “decay kelp” patches that mark toxin zones.

Fauna

Species	Behaviour	Threat level
Lava shrimp	Passive, near vents	None
Vent eel	Fast, electrical, hostile	High — multiple stings lethal
Ampeel	Predatory, attracted to light	High
Volcano leviathan	Apex predator	Extreme — attracted to heat

What’s dangerous

Three layered threats:

• Heat damage from the vents themselves. Even with the heat-immunity gene, sustained exposure drains your suit’s integrity.
• Toxin damage in decay zones. Even with the toxin-immunity gene, decay kelp touching you does damage.
• Volcano leviathan patrols the deeper parts of the band. It’s attracted to heat signatures, which makes vent biomes particularly dangerous.

How to survive

• Unlock heat immunity and toxin immunity genes before entering
• Bring the reinforced dive suit
• Stay close to vent walls; the volcano leviathan prefers open water
• Have an emergency exit route planned before entering any deep cave

Biome 5 — Deep abyss (1,500–3,000 m)

Endgame. Pitch black except for bioluminescent bacteria. Pressure is extreme. EA covers the upper portion of this band; deeper zones are coming in later updates.

Visual signature

Pure darkness. The water is so deep that no surface light reaches. The terrain is mostly rock, ruins, and emptiness.

Fauna

Species	Behaviour	Threat level
Abyssal scavengers	Passive, edible	None
Leviathan-class predators	Multiple species	Extreme
Precursor guardians	Stationary, defensive	High — protect precursor ruins

What’s dangerous

Everything in the abyss is dangerous. The biome is designed to be endgame.

• Pressure — even with all pressure-resistance genes unlocked, sustained dives are limited.
• Multiple leviathan species — at least two apex predators patrol this band.
• Precursor guardians — stationary but lethal if you get close.
• Disorientation — the dark, empty terrain makes navigation difficult.

How to survive

• Bring at least 2 pressure-resistance gene tiers
• Bring the pressure-rated dive suit
• Bring at least one full set of backup oxygen tanks
• Don’t dive alone. Always have a backup at the surface.
• Mark every ruin and feature with a beacon — it’s easy to get lost

Universal leviathan evasion tactics

Five tactics that work across every biome:

1. Lights off. Levis are attracted to light.
2. Engine off (in vehicles). Movement creates noise.
3. Drift, don’t swim. Slow movement = low wake = low aggro.
4. Use terrain. Caves, wrecks, coral ridges break line of sight.
5. Wait it out. Most leviathan patrols are 30–90 seconds. They’ll leave.

Universal danger responses

Threat	Response
Leviathan patrol	Lights off, drift, wait
Jellyfish colony	Light stick forward, slow swim
Bone shark pack	Swim vertically (up or down) to break formation
Crabsquid	Cut oxygen, drain battery, retreat
Vent eel	Don’t chase, let it disengage
Stalker	Drop metal decoy (advanced tactic), back off

Common issues and fixes

”I keep getting one-shotted by the Reaper in the sparse seafloor”

You’re moving too much or your lights are on. Both attract aggro. Stay still with lights off for 90 seconds and the Reaper will usually pass.

”The jellyfish keep killing me on the plateau”

You don’t have your light stick out. The jellyfish back off from sustained light. Pull out a light stick and hold it in front of you as you swim.

”The volcano leviathan follows me into the vent base”

You’re attracting it with the base’s heat signature. Build your vent base 20+ metres away from active vent mouths, so the base heat signature doesn’t combine with the vent heat.

”The deep abyss is impossible”

It is, until you’ve maxed your pressure resistance and brought a vehicle. Solo abyssal diving in starter gear is not a strategy; it’s a respawn loop.

Frequently asked questions

Q: Are leviathan patrol paths random? A: No — they follow fixed waypoints on a roughly 90-second cycle. The path itself doesn’t change, but the timing varies by 5–10 seconds.

Q: Can I kill a leviathan? A: No. EA has no combat weapons. Evasion is the only strategy.

Q: Do leviathans attack bases? A: Rarely, and only if their patrol path crosses the base. Choose your base site away from patrol paths.

Q: Are some biomes safer at night? A: No. Night makes every biome more dangerous because your lights are required but attract leviathans. Plan to be back at base by dusk.

Next steps

• Gene Modification System — DNA, the gene tree, tier strategy
• Resource Atlas — what spawns where, by depth band
• Tools & Equipment Priority — what to build, in what order
• Main Story Walkthrough — NOA, black boxes, precursor sites (coming soon)

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