Scientists at BYU's "Splash Lab" study the fluid dynamics of skipping rocks, which — judging from the water tanks and high-speed camera setups featured in this video — is every bit as awesome as it sounds.
Here, professor Tadd Truscott gives us a rundown on some of the basics of rock skipping, while Fuck Yeah Fluid Dynamics parses out the details on a couple of common skipping techniques:
In a conventional side-arm-launched skip, the rock's impact creates a cavity, whose edge the rock rides. This pitches the rock upward, creating a lifting force that launches the rock back up for another skip. Alternatively, you can launch a rock overhand with a strong backspin. The rock will go under the surface, but if there's enough spin on it, there will be sufficient circulation to create lift that brings the rock back up.