We’ve all seen it in movies: The hero needs to make a hasty escape, so he dives through the window into a nearby body of water. His pursuers, intent on killing him, reach the now-broken window and open fire, giving the audience a spectacular view of bullets ripping through the water all around our protagonist.
Even in the hyper-realistic “Saving Private Ryan” Omaha Beach scene we see this common movie trope in action, the camera submerging to show soldiers being riddled with bullets in the eerie quiet beneath the waves.
Although this common action shot in movies offers an incredible level of visual drama, it’s not actually all that true to life. Water is significantly denser than the air through which bullets are designed to travel, and the friction created by that denser mass has a habit of knocking bullets off of their trajectory, breaking them apart, or even stopping them in their tracks.
If you don’t have much experience with long-distance shooting, it can be easy to think bullets behave in the same way as laser beams: able to strike whatever the barrel is aimed at in point-and-click fashion. In real life, however, bullets are stuck abiding by the same laws of physics that apply to falling bowling balls and airplanes. In other words, bullets may be too small and moving too fast for you to see with the naked eye, but things like gravity, air resistance, and especially water resistance all have a significant effect on the trajectory of a round headed downrange.
Snipers that train to make exceptionally long shots have to take a number of variables into consideration beyond the concerns about wind speed and direction to which most shooters grow accustomed. Everything from the barometric pressure around you to the curvature of the earth itself must be accounted for when engaging targets from a mile out. Once you start to appreciate how much math it takes just to figure out where a bullet will go when traveling through air, it starts to make sense how rounds become a lot less predictable (and lethal) when traveling through far denser water.
In fact, water is about 800 times denser than the air we walk around in all day, which allows us to float on the surface with relative ease and, as European physicist Andreas Wahl set out to demonstrate, provides more than enough resistance to stop many bullets in their tracks.
As Wahl pulls the rope that fires the SIG SG 550, the waterproof ammunition fires the projectile with the same initial velocity of any other round, but as the bullet impacts the water and attempts to traverse the distance between the muzzle and Wahl’s bare chest, it sputters to a stop.
Sure, most of us would have been just as happy to see Wahl conduct this experiment with a ballistic gel dummy or maybe some watermelons as others have done in the past, but Wahl (who films a television show called “Life on the Line” for the Norwegian Broadcasting Corporation) has a flair for the dramatic as well as a mind for science.