Pykrete

Basic Information

Pykrete is a material made from 14% sawdust and 86% ice. It melts at significantly slower speeds than ordinary ice. During World War II, the British instigated Project Habakkuk to investigate whether it would be possible to build a floating aircraft carrier out of it (which would effectively have been unsinkable, since ice floats), but the project was scrapped due to its expense.

Sources

Max Perutz - father of molecular biology - background on one of the leading scientists of Project Habakkuk
Wikipedia entry

Game and Story Use

• If you can make an aircraft carrier out of this stuff, you can make anything with it. Perfect for the Floating Fortress of a ocean- or ice-themed supervillain.
• In fantasy games, it might be possible to make ice "permanent" with magic - in which case there could be huge floating barges or even fortresses made out of ice in the setting.