An older but common thread - can I shoot my Glock underwater. Mythbusters did an episode on this. So:

https://kitup.military.com/2017/04/s...nderwater.html

NATIONAL HARBOR, Maryland — A Norwegian company hopes the U.S. Navy will see the value in its revolutionary product: bullets that “swim” and remain effective on target for significant distances underwater.

The secret to DSG Technology’s CAV-X supercavitating bullets is a specially turned tip and carefully calibrated balance and mass, creating an air bubble that allows the munition to shoot through the water, said Kristian Aksnes, director of Special Operations Forces for DSG. The bullets are tungsten with a brass shell and designed to be fired from conventional weapons, he said.

While Aksnes said the technology is completely scalable, the company is offering the bullets in NATO 12.7, 7.62 and 5.56mm, as well as smaller calibers. The 12.7mm bullet, a machine gun round, has an effective range of 2,200 meters through the air and 60 meters underwater, according to the company. The 7.62 and 5.56 rifle rounds are effective underwater at 22 and 14 meters, respectively.
Now how to conceal your AR pistol in your speedo?