Pipedope, my problem with the air pocket that its something that should have been noticed and fixed right away. Im not complaining about, lets say, impossiblity of a dive to 20,000: they needed it for the plot, so it goes in, plausible or not. Movie law, like Kraken said. But the air pocket is just sloppy! And we all know, sloppy and diving do not mix. It voids the whole believability of that dive. Btw, did you notice that his light folded somewhere between 8000 and 20000? I would have thought if the light had a big air pocket (and it did cause some bubbles came up when it collapsed) it would have done it long before 8000 feet. More dramatic effect to fill the descent phase, I guess.
boomx5, I think they were using rebreathers for diving, which dont require large tanks. Not that I know anything about rebreathers.
Now I wish I had this movie on DVD so I could look at it again, because I thought they did have bubbles coming out of them
Which is probably the reason Bud did not have an octo to give to his wife.
Firebrand, I think they needed the Seals because of their special assignment: to prevent nukes from falling into the hands of the Russians. And you are right, they seemed completely unprepared for the situation, not physically but mentally. You could see it by the way that guy was driving the little sub.
Btw, I found an interesting thread online about liquid breathing if anyone is interested:
http://yarchive.net/med/liquid_breathe.html
I am trying to sift through and separate all the scientific postings from the pseudo-scientific ones. Not an easy task