@sagewolf8528

That would have been A lot of fun

@Aar0nDavis

It's a real shame. They should have kept it in, but I can understand why they cut it. I think there's a mod that puts Rapture into Fallout 4 though.

@JadianRadiator

Turns out the 20k leagues was horizontal distance.
With 20k leagues straight down placing you in the void of space past the other side of the Earth.

@labenv123

The whole story involved Zao telling the player he needs to reactivate reactors in the sub and head down below. A crash happens and ends up with Zao and the player exploring Vault 120, after the Sub gets lodged into the Vault entrance and now you explore a underwater vault partially flooded and full of robot security with windows showing the ocean. Heavily inspired by Bioshock. 
Later on, you'd walk on the ocean floor with a suit along with a harpoon gun, encountering mutated sealife and meet a survivor in the atrium area, all while restoring power and opening doors. Then able to meet the overseer, whos a giant talking octopus with telepathy behind a giant glass window. A Vault Tec experiment basically. 

Then you'd have the choice to spare him or activate a cycle to kill this Overseer. 
The player, Zao and this survivor would head up to the surface via escape pods and possibly, Zao would've been a Companion and the survivor a Settlement member.

@brookshennigan8886

They shouldn’t have cut it and then they should’ve made it DLC, but that’s incompetent Bethesda relying on its community to make its game for them

@sirbacon761

We need a dlc in Hawaii where we can have mutated sharks, sea creatures, and volcanoes.

@epikgaeymurs8244

Wonder how the residents got to the vault in time

@StreetSweeper1776

i will forever hate bethesda for cutting this quest out of fallout 4

@artg556

I feel sad for whoever suggested this idea and for those who were working on it, like, imagine spending 1/2 months doing a Quest and you have to stop and discard all your work.

@Swimmer218

I wonder why they cut this. It's a shame they did. I hope someone makes a mod or they release a DLC for this in the next one or an update for 4.

@majortom1155

I really like the idea of this quest that you have to team up with captain zao
Cuz he's a cool and really chill character that doesn't seem that much in the story
When i first play fallout 4 i didn't get the far harbor dlc and when i get one i was thinking wouldn't it be cool if we can ask zao to take us to the far harbor with his submarine

@CellaDragon

I can get cutting it for time constraints but I can’t get why not going back and finishing it later and uploading it as DLC. They like to do that shit

@themightybob

It makes sense that the vault with the highest number would be the cool one (that was cut)

@bapgames1

This is a great référence to french literrature.

@XYPE76

That would've been awesome, bioshock is one of my favorite games, along with fallout games. Atleast we still will get a somewhat hybrid of bioshock and fallout soon.

(Talking about atomic heart)

@scottwilliams7726

There is a mod that adds vault 120 on nexus. At adds an under water vault even a tv radio station

@Frigid_Knight

I smell some good content for a mod…

@Pylon.Boi03

Damn, why the fuck didn’t they include this in Far Harbour

@ImverytheoriginalMedjed

Fact is from what ive seen that quest wouldve been like a full ass dlc type shit but not like a real one

@ChronicBongitis420

If they don't put this in a game in the future they should do it in the show