Why couldn't they...? (SPOILERS)

Yes, you're right that flooding the sub would of course have increased the load -- the question is whether it would have done so to such an extent that the sub could no longer be held and would sink anyway. Remember that the sub was already mostly flooded anyway, so my guess is that flooding the small remaining portion would not have made much weight difference...certainly not enough to cause the sub to break from its raising platform and sink. Actually, the fact that the sub was already mostly flooded might have made a controlled flooding of the rest of it easier and less dangerous than had it been intact.

But again (and apologies for sounding like a broken record), the men were doomed by just releasing the sub, so what had they to lose by trying?

What gets me is that no possible suggestions for getting the men out were even discussed. Everyone was resigned to the notion that, if the sub wasn't raised in time, they'd have to release it and let them go to their deaths. No plan of action to avoid this was raised (if you'll pardon the expression). Wouldn't even a long-shot idea have been better than nothing? This self-induced resignation to the so-called inevitable -- which did not appear to me to be inevitable at all -- is baffling, annoying and depressing.

You make some good points but I still say that meekly accepting as inevitable the death of the three men without even trying to come up with an alternative is unrealistic.

The bends is an obvious hazard though not a certain one. As I said, the rescuers could have sent divers down to the sub equipped with oxygen lines or other breathing gear to give the men when they emerged and help them on their way up. Also, if necessary they could have decompressed the way early divers to the wreck of the Andrea Doria did, stopping at a certain level beneath the surface for a certain amount of time in order to decompress naturally. In the case of the Doria, which lies at a depth of 245 feet, it took divers about nine hours to decompress about 20 or 30 feet below the surface. For men ascending from only 30 feet, any decompression time would be much briefer than that, and like the Doria divers, the men could be continuously provided with air from hoses from the surface, and given a platform on which to rest, while they decompressed. If decompression was indeed necessary, it wouldn't have taken a long time.

Certainly any such operation entails risks (cold, hypothermia, the storm, sharks) and the men might have died anyway, but...well, you know, my oft-repeated question. They might have been killed in the attempt to flood the sub. But just try something! And to your last point, in the film it was explicitly stated that once the sub was let go there was no way the air would last long enough for a future rescue, so the men were doomed to die once the sub was dropped back to the bottom.

Couldn't a diver somehow have gotten into the sub and provided the men with breathing gear to get to the surface? After all, the crew got out of the sub by such a means. If they had access to a diving chamber I should think an outside diver could enter it, have the water pumped out and come aboard to help the men escape.

Alternatively I've also wondered why the rescue vessels had to let the sub go in the first place. Okay, a storm was coming. Couldn't they have ridden it out? Was it a certainty they'd lose the sub? Here again, the same old question, which this time I will repeat: What had they to lose?

Doing nothing should not have been an option.

There is so much misinformation stated in this thread--as well as in the movie--that I hardly know where to begin. First of all, 30 feet is not a problem for men without a breathing apparatus. Here is an excerpt from a Wikipedia article on the Momsen Lung, an improved version of the British breathing apparatus. It also discusses the breathing apparatus used in this film:

"The Royal Navy used a similar device, the Davis Submerged Escape Apparatus, but it was clumsy to use. The Royal Navy later adopted the practice of blow and go, in which the sailor would exhale continuously during ascent to avoid air expanding in the lungs, which could cause them to rupture. Postwar, submariner Walter F. Schlech, Jr., among others, examined submerged escape without breathing devices and discovered ascent was possible from as deep as 300 ft (91 m): "in one sense, the Momsen Lung concept may have killed far more submariners than it rescued."

The submariners had been in a submarine with fairly normal air pressure. They had not spent a lot of time at depth outside a vessel. So there would be no nitrogen narcosis to deal with. It would take only a short time to "blow and go" to reach the surface. They would have been fine, as long as they didn't panic.

The difference between stupidity and genius is that genius has its limits. -- A. Einstein