Can Guns Shoot Underwater?

can guns fire underwater

Maybe you’ve seen it happen before in movies or on TV where a character fires a gun underwater and successfully hits their target. Perhaps if you’ve seen one of these movie scenes before, you’ve been wondering just how realistic that sort of thing is and whether it’s even possible to fire a gun underwater at all.

In short, the answer is: it depends. Some guns can operate underwater while others can’t, and in almost all cases, the functionality of a gun is significantly reduced when firing it underwater.

So, if you’ve ever asked yourself “can guns shoot underwater”, then look no further for the answer; in this article, we’ll be debunking all the myths about using a gun underwater, as well as other related gun myths. 

Will a Gun Work Underwater?

As we’ve mentioned, some guns sort of work underwater, while others don’t work at all. When it comes down to it, there are factors that affect both the bullets and the gun itself that determine the effectiveness of firing a gun underwater. 

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How Bullets Are Affected by Water

As you know, for any kind of fire or explosion to occur, there need to be two things present; a fuel source, and oxygen. Knowing this, you may think that there’s no way a gun could ever fire underwater since there’s not enough oxygen present to ignite the gunpowder in the cartridge.

However, you would be wrong about that. Bullet cartridges contain both gunpowder and an oxidizing agent that gives the gunpowder the necessary oxygen it needs to combust. Bullets are designed to be completely airtight, and as long as the primer can be successfully detonated, a bullet can be fired in just about any environment.

However, once the bullet leaves the gun, things quickly change. Bullets fired on land are able to move quickly and travel great distances because the air offers relatively little resistance. Water, on the other hand, is about 800 times denser than air, and therefore any objects moving in water will encounter much greater resistance.

This means that a bullet fired underwater will start slowing down much more quickly than a bullet fired on land. While some guns can effectively hit targets from dozens or even hundreds of yards away when on land, underwater the maximum effective range of even the most powerful gun isn’t more than about 3 feet.

How Guns Are Affected by Water

The type of gun you’re using can also make a difference in whether it can operate underwater. 

Take a handgun, for example. Most handguns work in the following way; when the trigger is pulled, the hammer is released and strikes the firing pin, which in turn strikes the primer of the bullet, causing it to fire.

Some newer guns use “hammerless” designs where the hammer is hidden within the bodywork of the gun, but most older guns have exposed hammers that the user can pull directly. However, if you’re trying to fire a handgun underwater, an exposed hammer can make this a challenge.

The reason for this is the same reason that bullets can’t travel very far underwater: the resistance. When firing a handgun on land, the hammer only has to contend with air resistance and thus can move with enough force to detonate the cartridge’s primer.

On the other hand, when firing a handgun underwater, the hammer has to contend with a great deal of extra resistance. This can end up slowing the hammer down to the point where it is unable to strike the firing pin hard enough to fire a round.

Even if you’re able to successfully fire a gun underwater, it might still not operate as intended in other ways. In the case of semiautomatic handguns, like Glocks, the slide action probably wouldn’t work correctly due once again to the water’s resistance. 

Because of this resistance, the slide isn’t able to move backwards with enough force to complete the gun’s cycle of operation, meaning it would be unable to eject the spent cartridge and subsequently be unable to chamber a new round. If you were to try firing a gun like this underwater, you’d have to manually pull back the slide and chamber a new round each time you fired.

Even in the case of guns like the AK-47, which use a blowback system for full-auto firing, the force of the water surrounding the action would be too much for it to handle and the gun would be unable to cycle properly. 

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Are There Guns Made Specifically to Work in Water?

While the practicality of underwater guns may seem pretty limited (how often would you actually need to shoot something underwater?), there have been a number of guns developed over the years that have been optimized to work while fully submerged.

A common feature of most of these underwater guns is that instead of firing traditional bullets, they fire flechettes. A flechette is a pointed projectile with a vaned tail, slightly similar in appearance to a throwing dart. 

These guns obviously have a much longer effective range underwater than conventional firearms do, but the downside is that they don’t work as well on land, mainly due to the fact that most underwater guns use smoothbore barrels. 

Underwater guns are more powerful than spearguns, which makes them more suited for military applications. Both underwater rifles and underwater handguns have been developed; rifles are obviously more accurate and have a longer effective range, while handguns are easier to manipulate and aim.

Some underwater guns actually fire small rocket-powered projectiles, which retain more of their velocity in water and can even accelerate against the force of the water.

What About Firing a Gun From Land Into Water?

It’s more often in movies to see a villainous character firing a gun from land at the hero who is fully submerged in water. You see the bullets zip through the water as the hero desperately tries to avoid getting hit. But how much danger would the hero actually be in?

As it turns out, not that much. You might think that firing a gun from out of the water would give the bullet more time to accelerate and allow it to penetrate the water much more quickly, but in reality, bullets typically begin decelerating almost immediately after leaving the barrel of the gun. 

And of course, when the bullet hits the water, it begins decelerating even harder. A bullet needs to travel at a speed greater than about 200 feet per second (fps) to penetrate human skin. While being hit a bullet travelling at, say, 150 fps would be quite painful, odds are it would be a non-fatal wound. 

Even a .50 BMG round, which is a large, powerful round intended for heavy machine guns and anti-materiel rifles, will drop below 200 fps after travelling through just over 4.5′ of water.

So in real life, if you were trying to escape being shot by someone by submerging yourself in water, you would be perfectly safe from anything as long as you remained about 5-6′ below the water’s surface.

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What About Firing a Gun From Water Into the Air?

Firing a gun from water into the air presents its own set of challenges. Unless you make sure to clear the water from your barrel before firing, you could easily cause your gun to backfire and explode in your face.

When firing a gun in normal atmospheric conditions, any obstruction in the barrel can significantly increase the pressure on the internals of the gun when a round is fired. Usually, this happens when a bullet misfires and gets stuck partway through the barrel, but a small amount of water sitting inside the barrel can have the same effect.

If you’re attempting to fire a gun that has recently been submerged in water, you should take care to make sure the gun has been completely drained beforehand. Better yet, it’s a good idea in this situation to disassemble the gun and thoroughly clean it before attempting to fire it again. 

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