I believe that's a very technical dive with special gases, but do-able.
They abandon the vehical and use the submarine escape breathing appliance they can make it to the surface safely with No decompression sickness.
It would be shameful if the rescuers did do design in an escape for theselves.
HO HO HO all the way to the surface. (an i an't talkin bout no Sante Clause)
A Steinke hood, named for its inventor, is a device designed to aid escape from a sunken submarine, essentially an inflatable life jacket with a hood that completely encloses the wearer's head, trapping a bubble of breathing air. An advancement over its predecessor, the Momsen lung, it was standard equipment in all submarines of the United States Navy throughout the Cold War period. The US Navy plans to replace Steinke hoods in all US submarines with escape suits called Submarine Escape and Immersion Equipment by 2005.