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The M1 gun, also called the Mark 1 Mod 0 Underwater Defense Gun, is a firearm developed for underwater use by the United States military during the height of the Cold War with the Soviets. Like most other underwater guns, it was designed to fire a longer, streamlined projectile rather than a bullet. The M1 ammunition was engineered as a unique 4.25 inch dart made from a tungsten alloy. This was cataloged separately as Mark 59 underwater ammo. The projectile was a needle-like 0.1" diameter and weighed less than 10 grams. It also had four tail fins to ensure a...

The following is a science experiment conducted by Vite NRK do not try this at home. - It's harder to create movement in water than in air, because water molecules are closer together than air molecules. To show the difference in resistance, physicist Andreas Wahl from Viten NRK puts himself in front of a weapon submerged in water and fires it - on himself. Wahl's ballistic myth busting experiment and video evidence will have you second guessing all those underwater Hollywood action movie sequences. See it here.