Going for a walk, find a stream or small rescu. Select start site, and downstream - finish. At the start lower on the water makeshift boats: wood, bark, paper. You can also send in swimming different floating objects: sticks, twigs, leaves, etc., Now watch how the boat will sail faster and meet the winner at the finish. If the stream flows under a bridge or through a pipe, let the boats from one side of the obstacle, cross to the other side and wait, which one will appear first.