Nick Fiorenza writes: 

Rheinmetall has taken a concept dating from the end of the Cold War for countering the Warsaw Pact frogman threat and developed it to protect vessels and harbor installations against terrorist scuba divers -- anti-personnel depth charges to throw off ships moored in harbor.

The depth charges are deployed manually, activating three meters below surface and detonating at a depth of six to eight meters, killing frogmen with their shock waves or deterring them if they are further away. At a depth of around three meters, a hydrostat is activated to release the safety mechanism inside the fuze and a second hydrostat activates the firing mechanism at around six meters.

The 1.4 kilogram, 268 mm long depth charges are designed for easy and safe handling by untrained personnel. A diameter of only 60 mm allows for a good grip for throwing up to 15 meters. The only action required before use is to pull the pin, which unlike hand grenades does not activate the fuze by any time mechanism, Jan Schutte of Rheinmetall Waffe Munition, told DTI. Hydrostatic safety devices prevent accidental detonation and the charges feature a self-deactivating mechanism if thrown in water which is not deep enough.

A smaller and lighter underwater signal charge which is 145 mm long, weighs 800 grams and can be thrown up to 20 meters with the same safety features is designed for coded communications between surface ships and submarines.

The charges have been tested at the Rheinmetall facility in Unterluess, Germany. Because this is nowhere near the sea, the testing is done in vats, presumably without frogmen.

Schutte reports that the charges are fully qualified and in production, with several navies as customers, including the German navy.

The US Navy is testing a similar system called the Anti-Swimmer Grenade.

Credit: Rheinmetall Waffe Munition