A tarp is placed over the propeller of the submarine to prevent it from being photographed. A picture of the propeller, one of the very sensitive organs in the top secret nature of the submarine, would reveal information concerning the vibrations and sounds emitted by the boat which make up its signature. The first quality of a submarine is its absolute secrecy.

FRANCE. Cherbourg. May 10-20, 2010. Work and testing on the new ballistic nuclear missile-carrying submarine (SSBN) Le Terrible.