During an exercise, a sign on a bridge tells everyone "This bridge is
destroyed".
The exercise commences, and the Brig scans around with his binoculars.
Suddenly, he sees a line of soldiers walking over the closed bridge!
The General jumps in his Jeep and races down the hill to the bridge to have
a word with these subjects.
As he approaches, he can see that the first soldier in line carries a poster:
"We swim".