It was the dark days of World War II. Hitler's armies were at the apex of their power. The allies were losing thousands of tonnes of shipping to German U-Boats, threatening to strangle the war effort. They needed a secret weapon. They found Project Habakkuk. A 2,000 foot long, 300 foot wide aircraft carrier built of ice. Well, a mixture of wood pulp and ice, anyway. A plane-launching, U-Boat thumping motorized iceberg.
The ship was never built, but a small prototype was built in Alberta. The cost of the project was estimated at $70 million in 1942 dollars. That proved too rich for the British, especially for a ship made out of, well, ice.
Benefits: great for cocktail and/or skating parties. Drawbacks: its made of ice.
Thanks to MN for passing this along