The underwater vessel that might have been the inspiration for Captain Nemo‘s submarine, the Nautilus, in the Jules Verne classic 20,000 Leagues Under the Sea, has been discovered by a British explorer just off the coast of Panama beneath not 20,000 leagues but a mere three meters of water. As Steven Morris reports in a Guardian story, the cigar-shaped, cast-iron sub, The Explorer, originally constructed five years before Verne’s book for use by Union forces in the American Civil War, was found by Colonel John Blashford-Snell of the Scientific Exploration Society. Like the Nautilus, the Explorer “has a lock-out system, which allows submariners to leave, collect items from the seabed and then return to the vessel,” notes Morris. Says Blashford-Snell, “As far as I’m aware the Explorer possessed the world’s first lock-out system and its very uniqueness might have stimulated Verne’s imagination.”