The lost "Sub Marine Explorer,"

Jules Verne Nautilus real-life inspiration was found in the coasts of Panama

For the past 137 years, a mysterious wreck has emerged at low tide each day on a beach off the coast of Panama. Researchers now know that it's the presumed lost "Sub Marine Explorer," one of the world's first submarines and a vessel that would ultimately kill its German inventor.

The design reminded the scientist of an "iron cigar," and he instinctively thought of the "Nautilus," that legendary underwater vessel author Jules Verne described in his novel "20,000 Leagues Under the Sea."

the lost "Sub Marine Explorer," one of the world's first functioning underwater boats, designed by a brilliant German engineer whose invention eventually brought him an agonizing death.

The well-preserved wreck off the shores of San Telmo offers an unprecedented glimpse into the maritime past. Even though the beginnings of manned underwater vessels aren't so distant, the pioneer days of submarines remain filled with unanswered questions. Old construction plans often diverge from the actual designs, and many boats were either lost or destroyed. In some cases it remains unclear as to exactly how -- and whether -- the vehicles actually worked.

Only five diving machines from the years before 1870 have survived the ravages of time:

• The "Brandtaucher" designed by German inventor Wilhelm Bauer, now in a museum in Dresden.
• A nameless submarine used by the Confederates in 1862, during the American Civil War, now on display in New Orleans.
• The "H.L. Hunley," built in 1863 and currently being restored in Charleston, South Carolina.
• The "Intelligent Whale," a submarine built in 1866 and now in a New Jersey museum.
• And the "Sub Marine Explorer" off the coast of San Telmo in the Pacific, built in 1865.

The "Explorer" marks a high point in maritime engineering, but also a tragic one. Equipped with a cleverly designed system of ballast chambers and a compressed air tank that allowed for pressure compensation, it also had two hatches beneath the hull enabling divers to exit the craft underwater. But about 130 years ago, when the vessel was being used to collect oysters and pearls from the ocean floor off the coast of Panama, the condition known as "the bends," or decompression sickness, was largely unknown. The condition can cause an agonizing death when divers rise to the surface from deep water too quickly. Technical progress had fatally outpaced medical science, costing the inventor and team of the "Explorer" their health and their lives.

Little was known at the time about the man who designed the craft, a German inventor named Julius H. Kroehl who had emigrated to the United States. He built an iron fire watchtower in Harlem in 1865 and was then hired by the New York magistrate to demolish -- unsuccessfully, as it turned out -- a reef that obstructed shipping in the East River. But how did the mysterious German hit upon the idea of designing such a progressive diving ship?

A search through historical archives revealed that the "Sub Marine Explorer" last belonged to an outfit called the Pacific Pearl Company, which planned to dig for oysters off the coast of Panama in the 1860s.

As far back as the days of the Conquistadors, divers had been digging up treasures from the depths of the "Archipiélago de las Perlas." Black slaves had once fished the famed "La Peregrina" pearl -- a magnificent, softly shimmering 50-carat jewel -- from the waters of the archipelago. The shells also held the promise of fortune, offering wealth in the form of mother-of-pearl, a highly sought-after luxury material used in the fashion of the day.