Russia's trying to perfect guns that shoot underwater. That's hard.
Mainly because guns don't really work underwater.
Physics prevents normal bullets from traveling very far when submerged.
As War is Boring notes, Russia's been working on a solution for a few decades.
The first attempt in the '70s eventually produced the SPP-1M, a pistol with four barrels that shoots long, dart-like bullets.
Then came the APS, an automatic rifle that also shoots bullets resembling darts.
Both worked underwater. But because of the ammo, both had horrible range on land.
So Russia came up with a new gun: the ADS.
It uses different bullets and can be fired above ground and underwater.
When it comes to underwater firearms, Russia's pretty much on top.