Guide Steps
Step 1: Find cave entrances
Look for small cave openings in the Safe Shallows. These are tunnel-like structures in the rocky terrain, often marked by glowing flora. Crashfish nests are inside these caves. Bring a Seaglide for quick escape.
Step 2: Trigger the Crashfish
Approach the red, bulbous nest inside the cave. A Crashfish will emerge and chase you with an audible warning sound. Immediately swim backward and out of the cave. The Crashfish will explode after a short delay, dealing damage if you're too close.
Step 3: Collect the cave sulfur
After the Crashfish explodes, return to its nest. Cave sulfur is a yellow crystal-like substance left behind. Collect it quickly. Each nest yields 1 cave sulfur. Some caves contain 2–3 nests, but approach each one separately.
Step 4: Craft the repair tool
Fabricator → Equipment → Repair Tool. Requires: 1 cave sulfur + 1 titanium + 1 silicone rubber. The repair tool fixes damaged base modules, the escape pod, and eventually vehicles. It's essential before building any base.
Safety tip
Never enter a cave without a clear exit path. The Crashfish explosion does significant damage. Swim backward while facing the Crashfish so you can dodge. The Seaglide's speed helps you outrun the explosion radius. Don't try to kill the Crashfish — just trigger and retreat.