Patrols have to keep as many balls moving at the same time
One tennis ball per person, with a couple of spares. Patrols ideally the same size, as different numbers work differently well.
Tell the scouts that they cannot pass the ball to the person next to them, or to themselves. Other than that, they have to throw the balls to each other, starting with one, adding a ball each time they can deal with what they currently have.
Start with a couple of balls and build up to one ball per person, or more if you're adventurous!
With six scouts, the trick is to form two independent triangles, and all throw at the same time. The scouts should work this out.