Thanks Brent for the thoughts. You're right about scuba bubbles in the
tower, and with that I'll never get ALL the air out, but I should release
enough to mitigate the explosive release when the hatch is opened.
As for the little spare-air bottles, they are pretty much useless. As a
long time diver, trust me, nobody uses them. Depending on depth, you may get
only three breaths out of one. Not very useful if you are expending energy in a
stressful situation at say 100 ft. Much better to have small pony bottles ( not
full size 80's ) with regulators. I have one that I used for sizing my hatch,
and although it's pretty close, I can exit the sub with the pony tank, and at
100 ft, should have plenty of time to flood the sub, open the hatch, climb out,
and float up, with a short decompression stop on the way. If I'm the second
person out of the hatch, There's enough time for that too.
The only thing I don't like about the tank is... to fit through the
hatch I need to have the tank on my chest rather than on my back as in a regular
dive. It is easier to exit that way because I can see the bottle, valve etc. in
front of me and get out pretty easily, but it's not all that great when
ascending.
Also, a standard BC vest won't fit through the hatch, so I'll need to get a
couple of the old ''horse collar'' type.
I think a good addition if you really think that an exit is
likely would be a dry suit, or wet suit.
A wet suit will help you float up ( maybe too fast !) but a dry suit will
help you stay warm, even when you hit the surface.
This of course means you are anticipating a flooding, and in that case, you
probably shouldn't go down in the first place. Frank
D.