The shot of the ship on its side toward the end was an actual shot of the ocean liner SS Normandie, which had caught fire and capsized at its pier in New York. The fire was an accident, not sabotage (a cutting torch accidently set fire to some kapok life vests), though there were rumors of sabotage at the time.
Before he sold the property and the services of Alfred Hitchcock to Frank Lloyd Productions for $20,000, David O. Selznick had originally planned to film it himself with Gene Kelly, who had not as yet made a movie, in the leading role.
Alfred Hitchcock's original director's cameo was cut by order of the censors. He and his secretary played deaf-mute pedestrians. When Hitch's character made an apparently indecent proposal to her in sign language, she slapped his face. A more conventional cameo in front of a drugstore was substituted.
While being held in the library of Ms. Sutton, Kane was trying to signal Martin by highlighting a book title with his thumb. The books with ironic titles next to "ESCAPE" are: Method of Criminal Investigation, Coaster Captain, Sketch of a Sinner, The Rash Act, Conquerors of Time and Bad Company. Coaster Captain actually foretold the next sabotage event, which was in the NYC harbor.
The trivia item below may give away important plot points.
Alfred Hitchcock used the idea of "looks can be deceiving" throughout this entire film. Here are some examples - 1) Fire extinguisher filled with gasoline 2) Tobin playing with his granddaughter when Tobin is introduced 3)"Blind" Man Philip Martin who is "totally aware" of everything that is going on 4) Patricia Martin (Priscilla Lane) believing that Barry is a saboteur, because she believes he "looks" like a saboteur and he has a saboteur's disposition 5) The "little" major in Circus Caravan who is a "big" trouble maker 6) "Abandoned" Soda City 7) Freeman (Clem Bevans) believing Barry based on what he saw & the "surface" information Barry provided to him 8) Patricia Martin believing the Sheriff (Charles Halton) and his words 9)A party for charity affairs hosted by Mrs. Sutton (who secretly works with spies and saboteurs) 10) People ignoring Barry and his words (about Mrs. Sutton and others with her being spies and saboteurs) by saying that Barry is drunk and he is not even dressed 11) Barry and Patricia Martin are "trapped" at a public place (Mrs. Sutton's big party) 12) Patricia Martin using "lipstick" to write the information about her 13) The Cop not taking Barry and his words seriously about the ship being sabotaged 14) Frank Fry and the bomb detonator is inside a fake American newsreel truck. Another example in this film is the use of "an old fashioned peel telephone" in the visually "abandoned" office at Soda City. The message that comes through this old fashioned peel telephone is what matters. And not the physical appearance of the phone. Another interesting touch is Barry doesn't reveal anything about Patricia Martin to Freeman (Clem Bevans) in Soda City. But Barry later learns that Freeman knew far more than he did about Patricia Martin when they reach Mrs. Sutton's room.