Hi Alan. We have discussed this in the past, and we even had a
simulator at the convention three years ago, although it never made it into
the water. ( too cold )
We have some very experienced guys that will have something to say on
this, but here's what I remember from the past discussions.
People usually die when trying to exit a sub. Practice and a LOT of
good luck may help.
Scuba tanks ready to go need to be on hand inside and used during the
flood stage. It's going to hurt and you will break your ear drums if you're
lucky.
The air pocket in the sub must be released through a valve at the top,
or the hatch will "BLOW" open when pressure is equalized. Stay away from the
hatch when you open it.
Have a light ( or two ) because it's going to be dark, cold, and
scary.
Use scuba tanks large enough to supply the air volume for filling
the sub, blowing the hatch, fumbling around in the dark, waiting for the guy
ahead to get out, decompression stop on the way up, and some extra. The tank
needs to be small enough to get through the hatch with you. I'm looking at
the 40 cu. ft. ones as they are narrow and long, with a harness that mounts
them to your chest for getting through the hatch, and an inflatable "horse
collar" when you get to the surface to keep your face out of the water.
You'll most likely be unconscious by then.
Those little "spare air" things are worthless. You might get two
breaths out of one.
Doesn't sound like much fun, but MAYBE you live.
Frank D.