Joe Noble illustrates how submarine and magnetic mines work.
C/U newspaper headlines "More ships sunk by mines". Various shots of submarine mines in the Imperial War Museum with cartoons to explain how the mine is made and how it works to destroy shipping. Joe Noble illustrates by cartoons how mines are laid and swept with some actual scenes of minesweepers at sea. C/U newspaper headline "Planes drop mines over sea". Various shots of cartoons showing likely construction of magnetic mines, how they work and how they are laid and swept.