P-3 Orion deploying a sonobuoy. A sonobuoy is a portable sonar system used in anti-submarine warfare or underwater acoustic research.
More:
https://en.wikipedia.org/wiki/Sonobuoy
Previously:
steam-powered submarine
The H.L. Hunley, the first submarine to sink a warship
Disarming WW2 German mine - video
Bookmarks