The depth charge:
Germany’s success with submarines forced the British to innovate, and one successful result that is still in use today is the depth charge. This device is detonated by a pressuresensitive pistol; once the pistol senses it is at the correct depth by water pressure, it fires and triggers the explosives.
The first practical depth charge, the Type D, was produced by the Royal Navy’s Torpedo and Mine School in January 1916. The first German U-boat sunk by depth charge was the U-68, destroyed on March 22, 1916.