Typhoon relief: HMS Illustrious makes sea water fresh
23 November 2013 Last updated at 13:26 GMT
HMS Illustrious is on her way to the Philippines to help the survivors of Hurricane Haiyan.
She had been docked in Singapore, where she was loaded with 500 tons of supplies including food, water and helicopters.
The BBC's Jonah Fisher, on board the ship, found out how the navy turn sea water into drinking water.