Can underwater bullets penetrate thick armor?

A common misconception that general people believe is that a general bullet can travel underwater. This is probably because of Hollywood movies. Like the movie, “The Bourne Identity” when the main actor jumped into the water, bad guys shot bullets like crazy. But bullets were penetrating underwater like the air. There are tons of other movies like this that led people including me believing a general bullet will travel underwater like the air.

However, the reality is quite different. A general bullet will lose its power the moment it’s fired underwater. There are a number of YouTube video clips who actually tested it with a high-speed camera.

Check this video out first.

Check out “3:08” slow-motion video of a bullet trajectory in the water. It’s like the bullet hit a thick wall or something once it’s fired, then it lost its power substantially. This is what happens with a general bullet.

What would happen to an armor-piercing bullet when it’s fired underwater?  There were no video clips I could find on YouTube (which is understandable as it’s only for the military use.), but the answer is it will be exactly like a general bullet. In order to travel underwater, one needs to design ammunition in a special way. Typically, underwater bullets are called supercavitating bullets. 

Armor-Piercing bullet
Armor-Piercing bullet


If you’re curious about the supercavitating bullets, please read the below article for details. 


Now let me come back to the original question. Can underwater bullets penetrate thick armor? The answer is “No” and “Yes”. With typical underwater bullets, you can’t penetrate thick armor. But with GP bullet designed by Duretek, yes you can use underwater bullets for armor-piercing bullets. 

When Duretek designed the GP bullet, researchers’ goals are not only to support supercavitating features for underwater but also to increase its lethal power. Years of research we made it possible. There are two kinds of GP bullets. One of the underwater purposes, and the other for the armor-piercing purposes. However, they all are basically the same except the other is more powerful than the former. 

Check out the video below for details.

Imagine you could immobilize underwater mines with the GP bullet! The only way to find out is to try it by yourself.