“That comes later. The top priority is to attach an Oxygen line.”
The sub is bolted shut from the outside. Even if it had some hatch or something, at the depth of the Titanic wreckage, the pressure is ~6000 PSI. You can’t have an oxygen line because it would be crushed. If they are alive, the only way to save them is to raise it to the surface.
This was an ‘experimental sub’ ; listened to a lot of experts today; none said they would have gone down in that thing - they cut corners in design
Submersibles typically have ports on the outside specifically for an emergency oxygen line.
“The only way to save them is to raise it to the surface.” True. The pressure at 12,000 feet below sea level blocks other options. Prayers for the adventurers. Submarines can be fragile.