To begin, divide the kids into pairs. Make sure each group is balanced, and everyone is happy with their partners. The water balloon toss requires nimble fingers, and the ability to throw and catch flying objects with ease, so balance the groups out, and make sure there is no particular pair that is more skilled than the rest – e.g. distribute the more athletic kids equally, and do not pair them up with each other.
Next, distribute the balloons – one per pair. Instruct the kids to run to the tap, hose, or any other water source nearby, and fill their balloons with as much water as is possible. It is essential to make sure the kids fill the balloons up properly – the more the water, the thinner the skin of the balloon and the more liable it is to burst easily. Once the balloons are filled, instruct the kids to tie them up – help anyone who is having trouble with the knot.
Now, line the kids up side-by-side in two lines, with both lines facing each other – the partners should be face to face, directly in front of each other, and the distance between both lines should not be too wide at first. Make sure one partner is holding the water-filled balloon.
On your mark, instruct the kids to start tossing the water balloon back and forth between themselves and their partners. If anyone’s water balloon breaks, that pair is immediately out of the game. As the game progresses, gradually widen the distance between the two lines, so the process of tossing the water balloon back and forth becomes more difficult, and the kids have to toss further. In the end, the last pair left with an unbroken water balloon wins the game.