In April 2003, NASA's flagship Terra satellite spotted what appeared to be one of the largest Tsunamis ever recorded heading directly for Hong Kong.
There wasn't just one wave either, but at least four.
Experts measured the main wave at the time, and concluded it was more than 500ft-tall, ten times the size of the Indian Ocean Tsunami that killed at least 230,000 people.
The devastation it would have caused to Hong Kong, a city of 7 million people, was therefore clear to see.
But the wave never actually made landfall.
Scientists were reportedly baffled when the apparent Tsunami suddenly vanished into thin air, prompting a flurry of conspiracy theories as to what happened.
Now, a new Science Channel 'What on Earth?' documentary is exploring the theory that the waves might have been man-made, possibly a test of an "exotic" marine weapon.
A preview of the documentary, which can be seen above, features interviews with experts, some of whom put forward their evidence for the secret super weapon theory against others who say there was a computer glitch in the satellite imagery.