Iceberg saves Titanic!

Suggested indirectly by the linked idea.

It is quite widely known that the Titanic sunk after hitting an iceberg. It is also generally believed, but much less commented on, that the iceberg remained afloat after the incident, despite receiving quite significant damage. This simple fact speaks volumes, I think you will agree.

Clearly, it is not practicable for all ships to carry icebergs around as emergency buoyancy aids. Howevertheless, the necessary ingredients to make ice are generally close at hand, and the recipe is well known.

Proposed, therefore, is an emergency flotation system for stricken vessels. It consists of an intensely powerful refrigeration system, powered by an intensely powerful power source. A small nuclear reactor may suffice, and is already available as an option on some submarines. The refrigeration coils run in multiple loops just inside the outer hull. The multiple loops ensure that, if the coil is damaged at one point, that section can be isolated from the remainder.

As soon as the vessel starts to take on water, the emergency refrigeration system is turned on, slowly encasing the ship in its own personal iceberg, and providing emergency buoyancy.

Admittedly, this idea may be wildly impractical and require unrealistic levels of engineering; but it has its downsides too, such as the difficulty in steering the stricken (and now iceberg-encapsulated) ship effectively. However, we are English and will therefore persist.