A submarine escape plot was hatched to rescue him from exile in Saint Helena

Back in the early 19th Century, an Irish adventurer and smuggler named Tom Johnson hatched a plot to rescue the exiled Napoleon from his island prison on St. Helena. St. Helena was also guarded by the Royal Navy, along with a large garrison consisting of 2,800 men armed with 500 cannons. It was the perfect prison for the deposed Emperor one intended to keep him there permanently. But to do so he would need to approach the heavily guarded island with extreme caution.

That’s when he decided to design his very own submarine decades before the invention of the first practical underwater vessel. Called the Etna, the craft would have been 40 feet long and crewed by 34 men. It would also have been armed with torpedoes something Johnston had every intention of adding to his version of the underwater machine. Unfortunately for Europe’s sake Johnson’s plot was never realized.

The British were right to be worried that he’d escape. According to Dash, there’s enough historical evidence to suggest that this plan was very real. And in fact, Johnson likely devised the scheme after seeing a conceptual submarine design by Robert Fulton from 1806.