The Navy has developed a submarine escape trainer. Presumably, it assumes that your sub isn’t too deep.
But while I assume that it’s part of the training, I see no mention of the need to allow the air to flow out of your lungs as you ascend. The pressure in them at depth is going to be several times that at sea level, and if you hold it in, you’re guaranteed a pulmonary embolism, likely fatal. Also, surface rescuers would have to have a hyperbaric chamber handy, otherwise those rescued are almost certainly gong to get badly bent (again, possible fatal, certainly injurious), unless the accident from which they are escaping occurred shortly after submerging. But if you’re going to float around for awhile before being rescue, bends seem almost certain. On the other hand, I guess it still beats drowning or asphyxiation at depth. Sounds sort of like an ejection seat for an aircraft — attempted suicide to avoid certain death.
[Update a couple minutes later]
I don’t know what current training requirements are, but I think it would be worthwhile to give scuba training to all submariners, to reduce the chances that they’ll hold their breath while ascending. Rule number one of diving training is to never hold your breath underwater. Of course, it’s an easier rule to obey when you have an air supply…
[Update a few minutes later]
Yes, as corrected in comments, bends isn’t (aren’t?) an issue. I’d forgotten that subs are maintained at one atmosphere.