1942: Habbakuk was the code name for a secret British project to build a huge, unsinkable aircraft carrier. The project never got beyond research and the early stages of development, but if the vessel had been constructed, it would have been twice as long as the Queen Mary. Even more remarkable was the intended construction material – a frozen mixture of water and wood pulp. In essence, Habbakuk would have been a gigantic iceberg with a flat top to serve as a flight deck. The ice, of course, would have made it unsinkable; the wood pulp was for reinforcement.
Source: Georgina Ferry, Max Perutz and the Secret of Life (2007), pp. 98–110