So the Air Training Corps, Army cadets and the Navy cadets where on an expedition through some rough terrain. They were nearly at the campsite after a long days walk, exhausted and ready to keel over. The only problem was that there was a large river inbetween all the cadets and the campsite.
Being Navy cadets they all put the majority of their clothing into their bags and attempted to swim across the river. Half way across their bags began to let in water and they had to be abandoned or else be a risk to the survival of the cadets. Their bags floated down stream and were lost.
The army cadets put their heads together and thought about how to get past this water hazard without loosing all their kit like the Navy cadets. After some thinking the highest ranking cadet decided to sacrifice himself and as per the Navy cadets he swam through the river carrying a piece of rope. He managed to reach the other side and tied the rope to a tree... A cadet on the other side did the same. One after another the cadets put their bags and themselves on the rope and climbed along above the river. Unfortunately the rope broke and they too lost their bags to save themselves.
The Navy and Army cadets looked very miserable and then started to wonder where the Air cadets were. Not ones to miss out on getting warm the two cadet groups started walking, freezing cold, towards the campsite.
After about half an hour they reached the campsite and to their suprise saw the Air cadets sat there with their tents up and fires burning.
The highest ranking Army cadet walked up and said 'How the heck did you get across that river without getting soaked like the rest of us?'
One of the NCOs replied 'We simply took out our map, triangulated our position and saw that there was a bridge several hundred metres upstream'

Good ol ATC.