Where To Find Cave Sulfur in Subnautica (And How To Collect It Safely)

Cave sulfur is one of Subnautica's most essential early-game resources — and one of the trickiest to gather without losing your life in the process. If you've been searching crash-landed sections of the ocean floor and coming up empty, you're probably looking in the wrong places or missing the environmental cues that signal its presence.

Here's a clear breakdown of where cave sulfur spawns, what to watch for, and why your experience collecting it may differ significantly from someone else's playthrough.

What Is Cave Sulfur and Why Do You Need It?

Cave sulfur is a raw material in Subnautica used primarily to craft Repulsion Cannon ammunition, Pipe sections, and most importantly, Repair Tools — the latter being critical for fixing your Seamoth, Prawn Suit, and the Aurora's damaged systems.

It appears as small yellowish crystalline deposits and is almost always found near or on a specific hostile creature. That creature is the Crashfish — a small, fast, explosive organism that nests inside cave formations and charges at players when disturbed.

Understanding the Crashfish is the key to understanding where cave sulfur lives.

Primary Locations Where Cave Sulfur Spawns 🗺️

Cave sulfur doesn't spawn freely on the seafloor. It's tied almost entirely to Crashfish nests, which are found in specific biomes. These nests appear as narrow alcoves or crevices in rock faces, usually with a faint glow or visible Crashfish movement inside.

Biomes with reliable cave sulfur spawns:

• Safe Shallows — The most accessible early location. Nests appear in the rocky cave walls and reef formations, generally between 5–30 meters depth. This is where most new players first encounter cave sulfur.
• Kelp Forest — Nests are scattered through the dense forest environment, often tucked into the rocky substrate beneath the kelp canopy.
• Grassy Plateaus — Moderate depth range, with nests embedded in cave entrances and crevices along the plateau edges.
• Mushroom Forest — Nests appear here at slightly deeper ranges, typically 80–200 meters.
• Grand Reef — Deeper territory, with nests found along the steep cliff faces and overhangs.

The Safe Shallows and Kelp Forest are the go-to zones for players who need cave sulfur early without venturing into dangerous depth ranges.

How To Actually Collect It Without Dying

This is where most players run into trouble. The Crashfish defends its nest aggressively — it will launch out and self-destruct near you, dealing significant damage.

The standard collection method:

1. Spot the nest opening — look for a small cave hole, usually with a visible orange or yellowish Crashfish sitting inside.
2. Trigger the Crashfish by swimming close.
3. Immediately swim away at full speed — the Crashfish has a limited pursuit range and will detonate when it reaches its maximum distance or hits an object.
4. Return to the nest after the explosion — the cave sulfur deposit will be sitting in or just outside the nest alcove.
5. Pick it up with your right-click interaction before another Crashfish respawns (respawn timers vary).

Some players use the Seaglide to out-distance the Crashfish more easily. Others duck behind rock formations to let the creature detonate safely. Both approaches work — which one suits you depends on your current equipment and how far into the game you are.

Variables That Affect Your Cave Sulfur Runs

Not every player will have the same experience farming cave sulfur. Several factors shift how difficult or efficient the process feels:

Equipment stage: Without a Seaglide or high oxygen capacity, early cave sulfur runs in the Kelp Forest can be dangerous. Players still on basic tanks face a real time pressure that experienced players with upgraded tanks don't.

Game version and platform: The original Subnautica and Subnautica: Below Zero are separate games with different biome structures. Cave sulfur exists in the original Subnautica — Below Zero has its own resource set. If you're playing Below Zero and looking for the same material, you'll need to search for equivalent substitutes in that game's crafting trees.

Difficulty setting: On Survival and Hardcore modes, the damage from a Crashfish detonation is a genuine threat, especially early on. On Freedom mode, the reduced danger changes how cautiously you need to approach nests.

Nest density awareness: Nests aren't evenly distributed across a biome. Some sections of the Safe Shallows have clusters of three or four nests within short swimming distance of each other, while other areas are sparse. Learning the layout of your specific save file's terrain can make a significant difference in how long a cave sulfur run takes.

Quick Reference: Cave Sulfur Biome Comparison

What Affects How Much You'll Need

Cave sulfur isn't a high-volume resource — most players need it in small quantities, and a single run through the Safe Shallows or Kelp Forest typically yields enough for early crafting goals. That said, if you're repairing the Aurora extensively or crafting multiple tools, you may need several runs.

The amount you realistically need depends on which tech path you're following and how damaged your vehicles are — two factors that vary considerably depending on how you've been playing. 🧩