I’m not a total gun nut, but I do enjoy poking around the edges once in a while, and seeing what is out there. One of my regular stops is Forgotten Weapons, where I found this gem:
Today we have a manual for the Russian APS underwater assault rifle, thanks to our friend Hrachya. The APS (Avtomat Podvodnyj Spetsialnyj) was developed in the early 1970s as a way to provide greater firepower to Russian frogmen (who had been previously armed with knives and the SPP-1M underwater pistol). It was initially used by Russian armed forces, but has also been sold on the international market since the fall of the Soviet Union.
You can read more about this weapon, and in fact, download the manual for it.