The science of skipping stones

The tl;dr: hit the water at a 20% angle. But the answer isn't as interesting as the question"

Bocquet's quest to understand how this happens - how a solid object can skim along water without immediately sinking - began more than a decade ago, while he was skipping stones on the Tarn River in southern France with his young son. ''He turns to me,'' Bocquet says, ''and asks, 'Why does the stone bounce on the water?'"'' To answer that question satisfactorily, Bocquet and his colleagues built a mechanical stone skipper and analyzed the angle of each toss using high-speed video. They also created a set of mathematical equations to predict the number of skips.