Watch: Physicist Shoots Self Underwater

Physicist Andreas Wahl set up a high-powered assault rifle with a string tied to the trigger in a pool, waded a few feet down range, turned, stared into the barrel, and opened fire on himself. A bullet explodes out of the gun, ripping the water open in its wake, before lazily veering downward and sinking to the floor about halfway to his vulnerable human body.

Why risk life and limb like this, on video at that? Even as a calculated risk?

To make a point. Or, rather, to teach a science lesson: Water is 800 times denser than air.

This isn’t Wahl’s first foray into risking life and limb in the name of scientific education—he’s set himself on fire, and jumped from a tall height as well.