Walk to the nearest body of water and skip rocks. Count to 10.

How to do it

Drive or walk to the closest pond, lake, river, anywhere with still-ish water. Hunt flat, palm-sized rocks together. Demonstrate: sidearm throw, wrist flick, parallel to the water. Take turns. Don't leave until one of you gets to ten skips on a single throw. The look on their face is the whole point.