Cold water + wood pulp = Iceship!! http://www.dailymail.co.uk/sciencet...boat-sinks-sea-BBC-presenters-ship-melts.html If you have a boat made to go in cold waters such as the North Atlantic, maybe even the North Sea actually, then you can freeze water and hemp (or other material) to make a very cheap cargo ship or aircraft carrier. The large mass of such a ship combined with cold water means it will not melt. But, of course, if you make a small boat and put it in warmer waters then it will melt and sink: Pykrete was thought up during the Second World War when the Allies were running out of steel for ships. They decided that sticking wood pulp in ice would suffice, but the principle hasn't been put into action till this UK tvshow decided to test it out. I think they need to now think larger, and use colder waters, get this really tested! If proved it does show that colonisation of ice worlds can be done a lot easier than having to set up mining and refinery equipment on the planet before being able to build ships to transport required goods around the globe!