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.
i doubt they’d have time to drown tbh, at depth a small leak is likely to cause immediate and sudden implosion, instantly crushing anyone inside. not sure how that would play out in a larger non-circular space though like rapture.