A scene from The Secret of the Submarine. (Motography, August 26, 1916)
Top Secret Submarine Stuff
Dateline: August 1916
The release of the "Flying A" silent-movie serial, The Secret of the Submarine, was held back for a while because there was some concern that too many secrets were revealed in the filming. (This was during World War I.)
"The first chapter shows plainly the technical workings of a submarine never before displayed upon the screen. Although [the "Flying A"] had the cooperation of U.S. naval officers in the making of the picture, there apparently are some secrets not supposed to become public." – Motography, May 20, 1916
Eventually, the concerns were addressed, and the serial was released.