The first step in the Deep Sentinel program, one of the most ambitious ocean-engineering projects in decades, will be completed this year. This initial step, called Vanguard, will shelter three aquanaut-scientists at depths of 100 meters. Eventually, the project will create a modular underwater habitat system that will let scientists live underwater for weeks at a time.
Apparently when doing saturation diving like that you can’t even understand what the other person says, between the helium and the pressure the voice is too distorted to be intelligible.
You can communicate with a computer that transforms your voice to be intelligible but it is really not a pleasant conversation so you can stay there for weeks without having a conversation except for the bare minimum.