Icon cut content.pngThe following is based on Fallout 4 cut content.

20 Leagues Under the Sea is a cut quest in Fallout 4.

An unused Institute terminal entry (InstM02Terminal2Message) reads:

MS03 Temp Hydroponics Message


Access: Local. Login: ABinet.
Notes: Routine diagnostic on Courser designate X6-88, all functions nominal.
Access: Local. Login: ABinet.
Notes: More programming work on new AI software update.
Access: Local. Login: ABinet.
Notes: Prototype testing of neural net upgrades.


  • The editor ID and quest name can be found as part of the file name for the quest icon, but the corresponding values do not appear in the game files as a quest.
  • An unused marker named MS03ResurfaceMarker can be found in the game data.
  • The quest's Pip-Boy animation is the only occurrence of a living sea creature.
  • This would likely take place in an underwater vault as untextured assets can be found in the Creation Kit of both an underwater vault window (VltSquidWindow01) and an underwater vault door (VltLGDoorMarine01) can be found. Unused scripts refer to this vault as Vault 120.[verified]
  • An unused script titled DN158QuestScript has multiple references to some sort of submarine battle utilizing the Yangtze, with the player character loading and firing torpedoes at unmanned underwater vehicles while repairing damage to the submarine's rudder and fixing leaks onboard the craft.
  • Nahant would have been a major location in this quest.

Behind the scenes

The name of the quest is based on the novel Twenty Thousand Leagues Under the Sea by Jules Verne.

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