Enemies can be anywhere, so during the 1970s, the Soviet Union developed guns that could fire underwater. This selective fire rifle, the APS (Avtomat Podvodnyj Spetsialnyj), was among them. It could fire 5.66 mm darts from a 26-round magazine through a smoothbore barrel. The APS was deployed at least once:
The Russian government has publicly acknowledged only one instance of operational deployment. In November 1989 at Malta, President George Bush and Russian Premier Mikail Gorbachev had meetings aboard a ship and the flotilla on which these two heads of state met were protected by a 16-man team of divers armed with the APS underwater assault rifle.
Link and Video of an APS -via Outdoor Life | Photo: World Guns