Project Habbakuk

Project Habbakuk was a plan by the British during World War 2 to construct an aircraft carrier out of pykrete (a mixture of wood pulp and ice) for use against German U-boats in the mid-Atlantic. They even made a 60 feet prototype that took three years to melt. The project was however shelved due to rising costs, added requirements, and the availability of longer-range aircraft and escort carriers which closed the Mid-Atlantic gap that the project was intended to address.