Unless they are coming up on their own, it takes about 2.5 hours to get down to the wreck, and what I've read online is that these subs carry like edit:12 hours of oxygen. Docs on the submarine show 96 hours of oxygen, this was wrong of me to guess
They need to get a towing vessel to the area, they need to get the rescue sub down to the bottom, winch up, and get back up. 6 hours of work once you're there. That means they have less than 4.5 hours to get on station. It's 1000 miles from Boston. Ain't no ship in the world sailing at under 200 knots.
Bad news only from this. They gotta get up on their own.