DP-64.

This is coolbert:

Here from the wiki we have a description of a Russian one-of-a-kind weapon the specific purpose is to defeat the attack of the "frog-man ", the underwater combat swimmer, the under-water demolition operative, the saboteur attempting to destroy enemy ships while at anchorage.

The DP-64.

"The DP-64 is a Russian special-purpose double-barreled over/under grenade launcher designed to protect ships, dockyards, water development works, and other coastal installations from combat swimmers and naval special forces."

"these grenades act much like small depth charges, attacking submerged swimmers like true depth charges attack submersibles"

And from the web site: "Open Joint Stock Company 'V.A.Degtyarev Plant'”

"DP-64 grenade launcher is designated for protection of submarines in the above-water position, ships at external roadsteads, anchor stops and bases, for protection of water-development works and other sea and coastal installations against attacks of underwater combat swimmers."

The round as fired from the DP-64 analogous to a depth charge. Used against that military underwater combat diver whose mission is sabotage. Unconventional, asymmetric naval warfare as waged by American SEAL or Russian naval spetsnaz!

Developed by the Soviet in response to a lot of bad experience from that Angolan mis-adventure of the mid-1970's. Soviet, Cuban, and other communist nation flagged ships, civilian and military both [?] while at anchorage subjected to repeated successful attack and sabotage by underwater combat swimmers of unknown nationality [South African combat divers??]!!

That DP-64 a solution to a problem for which there was at the time no easy and instantaneous fix?

coolbert.