So why'd she do it? And what was her chosen mode of transportation?
Let's see ... it's 1966. The Beatles have achieved a certain amount of success with the teenage girl demographic ... the song "Yellow Submarine" has just come out ... ah, yes, it all makes sense.
It was a long and winding road, so being a day tripper, she got a ticket to ride. (Hey Jude).
"I like English boys," she would later tell police when asked her motive for stowing away inside a 1,600 ton British submarine. "I couldn't go legally, so I had to do it illegally."
She had slipped past officers guarding the sub, which was docked in Baltimore on a goodwill visit, tucking herself away inside a conning tower compartment of the HMS Walrus (yes, even reality couldn't resist adding bad Beatles references to the mix). She stayed in her spot for 12 hours before making her presence known, and then it was only due to the fact that she was on the edge of fainting from carbon monoxide fumes.
English boys prefer the rosy, deoxygenated look.