If you saw Captain America: The First Avenger, you know the movie is loaded with fantastic, retro-futuristic war machines dreamed up by supervillain Red Skull and his Hydra organization.

Discover how the filmmakers came up with one such vehicle — an escape sub used by a Hydra assassin — in the behind-the-scenes clip above.

Captain America’s lead vehicle designer Daniel Simon outlines several concepts that preceded the streamlined, cigar-shaped sub that made it into the movie.

“We could have gone totally overboard, but that would have made it almost childish, in a wonderful way,” says Simon in th...