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World 5 of 9

Unrailed!: Underwater (bonus) walkthrough

A bonus biome you reach through a hidden mineshaft in one of the first three biomes, with oxygen and exploding blowfish.

  • 2 parts · 10 steps

Compiled from 1 playthrough video and 7 guides · checked Oct 19, 2026

0 of 2 done
Video: TEC on YouTube (with commentary). Loads from youtube-nocookie.com only when you press play.

What each player can do here

P1 · Gatherer
  • Gatherer: holds the axe or the pickaxe, carries wood and iron to the Storage wagon, and grabs the bucket when the engine runs hot.
P2 · Track layer
  • Track layer: takes finished track off the Crafter, lays it ahead of the train, clears the path when no track is ready and deals with the creatures.

If your skill levels differ: The wiki and Blueprinted both say only one player should lay track, and a lower difficulty means more resources and less unbreakable rock.Our suggestionWhen skill levels differ: give track laying to the steadier player, and let the newer player own one tool and keep resources coming. How to split the roles

Finding the mineshaft

Part 1 of 2. How to get in, and what to do first.

  1. BothA mineshaft may appear on level 3, 4 or 5 of each of the first three biomes, and one is certain on level 6, 11, 16 and so on.
  2. BothIt sits by the streams of a waterfall; build track to the single rail inside it.
  3. BothIf you don't take it, it explodes when the next level loads.
  4. BothThe bonus biome exists only in Endless and Sandbox.
  5. BothPick up the orange special bolt before you go in, and buy what you need first: the shop is out of reach down there.single source

Down there

Part 2 of 2. Oxygen and blowfish.

  1. BothThe submarine engine adds no wagon slot, so you leave with the train you brought.
  2. BothYour oxygen drains while you are underwater.single source
  3. BothBlowfish swell up near players and burst like dynamite, hurting players and resources nearby.
  4. BothThrow dynamite at blowfish from a distance rather than walking up to them.single source
  5. GathererBlowfish milk gives infinite oxygen.
Sources (8)

Steps compiled from 1 playthrough video and 7 text guides, checked Oct 19, 2026, and written in our own words. We did not play the game for this guide. A step marked “single source” rests on one guide so far.