Started project to build expansive underwater city that would be fully furnished and be "Fully Independent"
The "city" has a few furnished houses with food and stuff.
A park in the middle
Air-lock on the other side of park
Would-be train station to other parts of the would-be city
Emergency air-locks that separates the home hubs from each other, these could be activated individually or at once from the park (I would have refined the circuitry to make it more fool proof)

If you want to get in and you are outside the cords for the Air-Lock is:

x: 16
y: 37
z: -70

I stopped spending time on this city because it was way too small

Now working on a MUCH larger underwater city
(Note: all the domes where constructed individually and not generated using WorldEdit, i quickly filled in some water using WorldEdit but it was quite resource intensive on the server so it took some time, that's the reason for the water not being everywhere (I will try to update the water later on))

This was a quick one day project with my friend though I ended up doing all the work, if you find a hole in the domes it was most likely endermen

Additional Notes

NOTE: A mod that disables water/lava dripping is HIGHLY recommended

(Such as Optifine)