Sounds very expensive for what it does.

This is so easy to accomplish. All boats should have a built in flotation system. The scariest thing on the water these days are those giant cruise ships, death trap want a be and polluter extraordinaire.

@ Rehab Do you wear a helmet when you step out of the shower? One is far more likely to die from a head injuries sustained from slipping coming out of the shower than having a cruise ship suffer enough damage to need the support of the balloons. As for the pollution generated by the ship consider what the people would be doing otherwise and how many would be using electricity generated by burning coal instead of Bunker C. Sense the ship has to have a sewage treatment plant on board or pump the sewage off while at port they do so because the fine for getting caught dumping raw sewage at sea is much more expensive. Likewise they have to pay for garbage disposal at ports so why dump at sea?

The much illustrated Costa Concordia shipwreck rarely shows the relatively small gash in the side of the vessel. Clearly these top-heavy vessels have an intrinsic design flaw so that when they are flooded there are no bulkheads to prevent the water flowing from port to starboard and when it does the vessel capsizes. This obvious flaw effects the entire fleet of modern cruse ships and yet is being occulted from plain view in the case of this ships disaster by focusing attention of the shenanigans of the captain instead. What should happen is the fleet be taken out of operation until new bulkheads are installed of the ships scrapped.
See: http://www.telegraph.co.uk/comment/columnists/christopherbooker/9030330/The-EU-ignored-years-of-expert-warnings-on-cruise-ship-safety.html

These giant ships are far too top heavy and far too under-engineered for their size. Literally, the design and management flaws that produced the Titanic disaster are being repeated. Titanic's builders and ship architect both knew that their rivets and plates would become brittle in cold water. They almost did the test that would have shown this but they though that the increase in brittleness was linear and not logarithymic. Big Mistake. Today's architects think they have systems design, compartmentalization, & stability down to a perfect science. The Costa Concordia, other numerous minor fires that shut down ALL power on several sequential cruise ships and even the Korean capsizing all show that everyone is pushing the envelope too far.

Roughly 25 years ago after a highly publicized incident in the Persian Gulf in which the USS Stark was almost sunk by an Exocet missile fired from an Iraqi owned Mirage fighter, I determined I would invent a system that would prevent ships at sea from ever sinking. And I succeeded. With my system in place no ship large or small need ever sink anywhere in the world. In fact I claim if a ship fitted with my system broke in half, both halves would float. What is this system? In a word "Airbags", in a sinking situation airbags would pop out of containers fixed to bulkheads in the affected compartments. As the airbags fill with air they displace any water and prevent the compartment from flooding. Repeat for all affected compartments. Not only would the ship not sink but there would be almost no danger of capsizing. And further Navy ships could remain on station doing there job until relieved. I wrote or called every civilian ship builder and cruise line I could find and offered this system for free since it's a life saving device. To date I have been completely ignored. I also contacted the US Navy and was directed to the Department of Naval Research. I got a call back from them and I'll never forget the conversation I had with the young captain. After a lengthy explanation of how the system would work she acknowledged that it would work as described but she said and I quote "The Navy will never go for it because every time a ship sinks, they get to build a new one". Imagine how patriotic I felt right at that moment. Imagine how warm and fuzzy I felt when the Costa Concordia sank or how I felt when that South Korean ferry sank killing all those high school students. These ships didn't have to sink and these people didn't have to die! But because I poses absolutely no credentials no one will listen to me. Thanks a lot E.U. and the SU SY Project! Lives will finally be saved but don't come along and claim to have any precedence here . I invented the whole concept over twenty years ago and I would put my concept against this one any day.

David Richard Tobin and StWils are so right. The solution in my view would be that no ship should be given its certificate of seaworthiness until its stability under full load operating conditions has been demonstrated with the three or four compartments, or damage as Concordia, fully flooded. It's all very well for the designers to posit that it's all a matter of the shift in the metacentre after such damage, as if the situation were beyond their control of the design, but behaviour after damage is the most elementary of all safety considerations. One wonders how many of the passengers would be happy knowing just how the stability is calculated to be satisfactory, or where the metacentre may be in relation to the ship's CofG even under "normal" sailing conditions. Rocks and sandbanks are only one of the hazards that seem to be ignored and super waves breaking glass and flooding upper decks never seem to be considered either. As in all engineering matters, it's all a matter of detail in the fitness for purpose. Concepts are not enough.

Why put them in the inside of the hull? Retrofit existing ships with canisters affixed to the outside and inflate them as needed after a hull breach. Inflate only enough to stabilize the ship and allow for evacuation. It also solves the thermal issue since the heat would be dissipated to the water and not kept inside the hull.

The Concordia could have survived the the hull breaches but she couldn't survive the captain's incompetence. The moron ran aground and then ran away. Simply counterflooding or shifting "cargo" to the opposite rail could have kept her upright until they patched the hull.
@ Russell Poley The Navy 0fficer was telling you to stop wasting their time and inventors are typically immune to logical arguments against their invention so they told you a lie that you couldn't counter.

@ Slowburn
You would be right except for a few points. First, it absolutely will work exactly as stated, It wouldn't be prohibitively expensive, most ships could be retrofitted with it and saving lives is clearly not a waste of time. Also, the person I spoke with was only a captain and so had neither the authority to say yes or, unfortunately, the courage to pass it on to her supervisors.
As I said originally I'm glad lives will finally be saved but frustrated that it took 20 plus years and by my rough count, over a dozen major ships and over one thousand lives lost.
P.S. There are some ships that still scare me. Ore carriers since they are already filled with very heavy cargo and propane or natural gas tankers because of the risk of catastrophic explosion.