Using a small fire and small billy, boil some water
Tinder, wood, matches, billys (varying sizes)
In patrols Scouts are to start a small fire. They will be given a contraption to hold a billy over the fire when it is ready. The winning patrol is the first to successfully boil water.
Scouts use a steel to start the fire
Try and give Scouts the option of different sized billys and highlight the fact that the more water you have the longer it takes to boil.
Watch out for clever Scouts using the kettle!