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A flat stone, a still lake, late afternoon. Pull back from the stone and let go. Flat and fast skips; steep sinks. Spin keeps it level, so a long smooth pull throws better than a hard jerk.

Physicists threw aluminium discs at a water tank in 2004 and found a "magic angle": the stone skips most when it meets the water tilted about 20 degrees. Here the contact angle is the angle of the stone's path, and it skips only below about 28 degrees, and best near 20. Each touch loses some speed and spin, so the skips get shorter and closer together, the way real ones bunch up at the end, a little run of pitty-pat-pat before it goes under.

The record is 88 skips, Kurt Steiner, Pennsylvania, 2013. Nobody here is getting 88.