For the past 140 years, a mysterious shipwreck has appeared every day at low tide in an isolated cove on the uninhabited island of San Telmo along the coast of Panama’s Pearl Island archipelago. Journalist and world traveler, Jeff Campagna, explores the history of this strange submarine, a revolutionary vessel that ultimately killed its brilliant German inventor. Campagna also delves deep into the early history of pearl diving in one of the most remote clusters of islands on Earth.


Taking off from the small runway at Albrook airport in downtown Panama City, it’s just a short fifteen minute flight southeast over the gaping mouth of the Panama Canal. Over the hulking cargo ships that are waiting in the bay for passage, over the seemingly endless turquoise waters of the Gulf of Panama, to the Pearl Islands — a paradisiacal archipelago of some 200 islands a mere thirty miles away from civilization.

Outside the foggy airplane window, some of the smaller islands begin to reveal themselves like tiny cigarette burns on bright blue silk. And then larger islands. Most of them swathed in virgin rainforest. Some of them ringed by sandy white halos. Hundreds of years ago, these scattered mounds were known for two things: the rich pearl beds lurking in their waters and the menacing pirates lying low in their coves.

Isla Contadora, the most notable in the archipelago, opens up before us as we descend. Our Piper Cherokee Six kisses the tarmac with a skid. From the quiet tourist beach at the base of the runway, it’s another twenty miles in a rusted panga to the shores of the uninhabited island of San Telmo where a mysterious shipwreck has been beached and forgotten about for almost 150 years.

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On an afternoon in 2001, Jim Delgado sat waiting for the tide to go out. A local Panamanian fisherman had told him a story that a Japanese submarine from World War II was rusting in a nearby inlet and it appeared each day during low tide. The story was hard to believe. What would a Japanese sub be doing in Panama? But Delgado was a marine archaeologist. He’d written thirty-two books about artifacts that lurk in the deep blue abyss. He was the Executive Director of the Vancouver Maritime Museum in British Colombia. He had worked countless shipwrecks before. Some of which were thousands of years old. Others dating more recently to the Cold War. And although Delgado was simply on vacation at the time, he just had to investigate the fisherman’s tale. But the tide was still high. The shipwreck was nowhere in sight. And so Jim Delgado waited.

The rusted conning tower was the first thing he saw. And the shadowy likeness of the hull, still just below the surface, tantalizingly obscured by a few feet of water. As the tide slowly slipped away, the upper hatch — orange and brown with corrosion — revealed itself in full. “As I looked out, I saw it appear in the water. When I saw the stubby, cigar-shaped submarine, I knew it was not Japanese,” Delgado states with a chuckle. “I knew it was old and I knew that it had a story to tell.” It looked like nothing he had ever seen. Soon, Delgado stripped down to his boxers, grabbed his cheap point-and-shoot, and began wading out into the warm salt water to get a closer look.

He didn’t have a measuring tape. He didn’t have any of his tools, for that matter. But that didn’t stop him. He was up to his chest in water and the waves were crashing up against the hull. Delgado squinted to see through the spray. He could tell that the 40-foot-long football-shaped sub was firmly embedded into the sand. He crawled inside through one of the rusted openings in the upper half of the hull. He cut his leg against a sharp piece of corroded metal. Blood began to seep into the crystal blue salt water. But Delgado barely noticed. His first assumption was that the craft had been built around 1900, but now, on the inside, he found that the metal had been forged with a heavy hammer: a clue that the manufacturing date was closer to the 1850′s.

The Sub Marine Explorer at mid-tide.
The Sub Marine Explorer at mid-tide

He crawled out of the sub, again nicking himself. Still not ready to leave, Delgado scrambled up the side of the hull and reached the conning tower (which must’ve lost its hatch door long, long ago). As he looked down into the dark cavern of the sub, he could hear the surf booming against the side of the hull. He could feel the metal resonate. He squeezed himself into the opening and fell blindly into waist deep water. Much to his surprise, he was in an entirely different section of the sub. What did they use this thing for? Delgado thought to himself. Just then, a panga approached to take him back to the cruise ship.

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Back home, Delgado was bewitched by the discovery. He had emailed photos of the sub to historians, fellow marine archeologists and antique submarine enthusiasts around the world — but no one knew anything about the vessel. No one had seen anything like it before. One researcher, Gene Canfield, mentioned to Delgado that the sub looked similar to theIntelligent Whale, a submarine built for the Union Navy during the Civil War in 1863. But the Intelligent Whale was supposedly never completed. And could the Panama sub even be that old?

In 2003, there was a break in the case. Rich Wills, an underwater archeologist, suggested to Delgado that the Panama sub resembled yet another long-forgotten Civil War submarine called the Sub Marine Explorer. It had been built for The Pacific Pearl Company for harvesting pearls from deepwater oyster beds. But no one knew what became of the Sub Marine Explorer. It had just disappeared from history. Could this be it? Delgado thought to himself. How could an iron sub survive almost a century and a half on a tropical beach withstanding the pounding of salt water tides and tropical surf? Wills sent Delgado a rare article on the history of U.S. submarine development that was published in 1902 in the Journal of the American Society of Naval Engineers. The article contained blueprints of the Sub Marine Explorer. It listed the dimensions of the craft and described the somewhat odd bulges in the hull near the conning tower. The descriptions were a perfect match.

Ink drawing of the Sub Marine Explorer by John McKay, 2007
Ink drawing of the Sub Marine Explorer by John McKay, 2007

Only five diving machines from the years prior to 1870 have managed to survive the centuries: the Brandtaucher, designed by German inventor Wilhelm Bauer, now in a museum in Dresden; an unnamed submarine used by the Confederates in 1862 during the American Civil War, now on display in New Orleans; the H.L. Hunley which was manufactured in 1863 and on display in Charleston, South Carolina; the Intelligent Whale, a submarine that was built in 1866 and now resides in a New Jersey museum; and, last but not least, the Sub Marine Explorer, built in 1865 and now laying at rest, half-embedded in the sand some fifty miles from Panama City, rusted and forgotten.

Delgado believes that war spurs both terrible and magnificent inventions, and the Sub Marine Explorer is one such example. The Civil War compelled both the Confederacy and the Union to explore submersible weaponry. Inadequate understanding of the technology sent many inventors and their crews to watery graves during the process. Julius Kroehl, a German-born American inventor and engineer, learned all he needed to during the Civil War to apply his submersible expertise to more commercial efforts when the war began winding down.

Kroehl was the chief engineer and a shareholder in the Pacific Pearl Company along with two partners, John Chadwick who served as the company’s president and George Wrightson, who served as treasurer (some public business records even list the famous W.H. Tiffany as a partner). The company’s primary objective was to harvest pearls from Pacific ocean beds. In 1865, Kroehl began building the Sub Marine Explorerin the Perrine shipyard on the banks of the East River in New York City and, when it was completed the following year, tested his invention in front of a gathering of curious onlookers and skeptic investors in the Brooklyn Navy Yard. Upon resurfacing, Kroehl presented the audience with a souvenir he had brought back from the bottom of the river: a bucket of East River sludge. In March of 1867, the inventor set sail from New York City to Panama’s Atlantic coast with a small crew and his beloved submarine that had been disassembled for the journey and packed into wooden crates.

After almost half a year at sea, Kroehl and his crew disembarked at the Atlantic Terminal of the Panama Canal Railway in Cólon. For a number of years, early in its history, the sizeable United States émigré community called the town Aspinwall after William Henry Aspinwall, the prominent Panama Railroad promoter. But the city’s Hispanic community insisted on calling the town Colón in honor of Christopher Columbus. The town itself was simple. The population: barely 3,000 people. But Kroehl wasn’t playing tourist. He was committed to seeing his mission through to the end. With the help of a massive steam-powered crane, the crated submarine parts were transferred from the ship’s cargo hold into a collection of railroad cars. It took the crew the better part of a day to cut fifty miles through the inhospitable jungle by rail, across rivers and ravines beneath rainforest canopies that blocked out the sun and down the rolling mountains to the Pacific shore of Panama City.

In December, the Panama Star and Herald reported, “A new diving apparatus, intended for Pearl fishing in this bay has been recently brought out from New York, and is now in course of construction at the Railroad Station. It is a boat about 36 feet in length, constructed in such a way as to be capable of propulsion at a depth of several fathoms under water, and persons can remain working below for several hours in succession. The apparatus will be complete within two months.”

Unfortunately, it took Kroehl and his men a little longer than two months to reassemble the Sub Marine Explorer (often referred to as the Explorer). An outbreak of yellow fever claimed the life of one of his men. Then, the funds dried up. Kroehl had incurred upwards up US$30,000 in expenses while in Panama and his partners back in New York City weren’t all that keen on sending more capital down to the tropics. A Panama-based correspondent for the New York Times reported that the Pacific Pearl Company had “come to the conclusion that men ought to be willing to work for glory in Panama.” But after a journalist from The Brooklyn Daily Eagle wrote that, “many persons think that the Pacific Pearl Company will secure untold wealth,” the funding was revived. In May, over a year since leaving the port of New York, Kroehl had finally put his beast back together again much to the delight of the press.

“The sub-marine boat Explorer was most successfully launched from the Railroad Company’s works on Wednesday, the 29th, under the superintendence of her builder, Mr. Kroehl, and can now be seen afloat off the wharf,” the Panama Star and Herald announced. “In a few days she will be taken to the Pacific Mail Steamship Company’s islands, where the experiment of submerging her will take place. Skeptics are now tolerably well satisfied that the Explorer can perform all that her builder has promised, and few of them would be willing to risk a bet against her thorough success.”

Off the coast of Isla Flamenco, four miles from Panama’s mainland, Kroehl and his crew carried out the experiments with great success. On June 2oth, they took the Explorer down to three and a half fathoms and remained at that depth for an hour. During an experiment two days later, the Explorer made it to four fathoms with Kroehl and four assistants onboard as well as a curious local ship captain. Watching from the shore was the President of the State, General Olarte, the Secretary of State, Mr. Bermudez and some twenty other invited guests who all applauded enthusiastically as the Explorer’s conning tower resurfaced like a creature from the deep. Shortly after, the Explorer and her crew shipped off fifty miles southeast, past the main island of Contadora, to the small, untouched isle of San Telmo on a doomed search for oysters and pearls.

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Julius Kroehl may have been an undersea pioneer, but he was certainly not the first hopeful to sail to the archipelago looking for fortune. When the Spanish adventurer Vasco Nuñez de Balboa crossed the Isthmus of Panama in 1513, becoming the first European to reach the Pacific Ocean from the New World, his main motivation was accumulating riches for himself and his sovereign, King Ferdinand II.

Balboa claims the "South Sea"
Vasco Nuñez de Balboa claiming the “South Sea” for Spain

While Balboa and his 190 Spaniards stormed through the thick, virgin rainforest of Panama, killing natives and razing entire villages, the conquistador managed to convince Tumaco, a fleeing cacique (chief), to stay behind. In return for sparing his life, Tumaco presented Balboa with gold and a basin of 240 extraordinarily large black-lipped pearl oysters. But it surprised Tumaco when the Spaniard showed more interest in the pearl than the meat of the oyster itself. As it turned out, tribesmen in the jungle had been unknowingly sabotaging valuable pearls for generations by roasting oysters over open fires at dinner time. Tumaco spoke of another sea beyond the jungle and mountains, a sea that was easily navigated by canoes, a sea that was rich in black-lipped oysters. Balboa wrote to the King about what he had learned from the natives he encountered on his travels across the isthmus. “I believe that there are many islands in that sea,” Balboa wrote. “Natives say that there are many large pearls, and that the caciques have baskets of them. It is a most astonishing thing and without equal, that our Lord has made this land.” Upon reaching these islands by canoe, Balboa named the groupArchipiélago de las Perlas (the Pearl Islands).

Balboa soon realized, however, that although the natives in the jungles on the mainland simply chucked the pearl into the dirt after eating the oyster’s meat, life for the natives on the islands practically revolved around diving for valuable pearls. The islanders, led by their particularly fierce cacique, Terarequí, were not about to hand over their land quietly, and so the Spaniards returned to the islands with a greater force, killed Terarequí and enslaved the natives of the archipelago.

The ancient Panama Pearl fishery. Photo courtesy of J.P. Delgado
The ancient Panama Pearl fishery. Photo courtesy of J.P. Delgado

Over the next century, the Spanish transformed the windswept islands of the archipelago from places of peace and plenty to hostile island prison camps. The natives were dragged onto boats and forced to show the Spanish where the oyster beds were. The Spanish would then tie heavy rocks to the divers’ feet, hand them a sack and a knife, and send them overboard. Hurtling down to breath-hold limits under tremendous water pressure, the slave-divers would collect as many oysters as they could before using the knife to cut the heavy rock free and rise to the surface. But not every oyster has a pearl. On the boat, the Spaniards would shuck the oysters and send the divers back down if there were no pearls in their yield. Soon, the shallow oyster beds located near the islands were picked dry and so the slaves were forced to dive to even deeper oyster beds farther out at sea — sometimes as deep as seven fathoms. The divers would often resurface with blood streaming from their ears, nose and mouth from the pressure. The natives began to slowly die out from European diseases and brutal overwork. By the sixteenth century, they were totally extinct. It took more than eviscerating a native population to dissuade the Spanish. They began importing black slaves from Africa to take over the dangerous diving work. The descendants of these slaves still populate the archipelago to this very day.

Slave divers harvested some of the world’s most sought after pearls during this time. Perhaps the most famous was the Wanderer Pearl (La Peregrina). The 55.95 carat pear-shaped pearl was found by an African slave off the coast of Isla Santa Margarita and then brought to Don Pedro de Temez — the administrator of the Spanish colony in Panama. Temez personally brought the Wanderer Pearl to Spain and presented it to the future Phillip II of Spain who gave it to his wife, Mary I of England. After Mary’s death in 1558, the pearl was returned to the Crown of Spain where it remained part of the crown jewelry for over 250 years. Joseph Bonaparte, elder brother to his more famous sibling, Napoleon, was installed as the King of Spain in 1808. After a five-year rule, Joseph was forced to flee the kingdom. But before leaving, he took a keepsake: the pearl from the crown jewels. It was then that the pearl got its nickname, the Wanderer.

In his will, Joseph Bonaparte bequeathed the pearl to his nephew, the future Napoleon III of France who, while exiled in England, sold it to James Hamilton, Marquess and later Duke of Abercorn. Hamilton’s wife, Louisa lost the pearl on two occasions — once in the sofa cushions at Windsor Castle and again at a ball in Buckingham Palace. Both times, the famous pearl was recovered. In 1969, the Hamilton family sold the pearl at a Sotheby’s auction in London for $37,000 (over a quarter million dollars today). The buyer? Hollywood A-Lister, Richard Burton, who presented the Wanderer Pearl to his wife, Elizabeth Taylor, as a Valentine’s Day gift during their first marriage. In a Christies auction in 2011, the pearl sold again, this time for more than $11 million, though its value had only been estimated at $3 million. The African slave who resurfaced with the Wanderer Pearl more than 400 years ago was rewarded with his freedom.

Mary I of England in 1554, Margaret Queen of Spain, 1606 and Elizabeth Taylor, 1969 all wearing the La Peregrina pendant.
Mary I of England in 1554, Margaret Queen of Spain, 1606 and Elizabeth Taylor, 1969 all wearing La Peregrina

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Jim Delgado returned to the site of the wreck in 2002 and again in 2004.The Explorer was always a gnawing distraction. He knew damned well that as each day passed, the sandy tides and salty waters further eroded the answers that waited within her rusted hull. That lonely iron vessel almost 4,000 miles away was always on his mind. But it wasn’t until 2006 that Delgado returned to the island of San Telmo with a fully outfitted expedition underwritten by Eco-Nova Productions Ltd., the Canadian producers behind the National Geographic Television Series, The Sea Hunters.

Accompanying Delgado on the expedition was Australian, Michael McCarthy, a world-renowned underwater archaeologist, Larry Murphy, a specialist in corrosion studies and metallurgist Don Johnson, a respected expert in the study of materials and rust processes. This time, Delgado and his team were well-equipped with GPS navigation gear, multi-parameter probes and laser-guided distance measuring devices. The team was determined to unearth all the secrets that Julius Kroehl’s invention had to offer. After all, the Sub Marine Explorer represented a crowning-point in 19th century maritime engineering. Many of the subs around the same age as the Explorer had been lost, destroyed or sunk. All those mysteries never to be solved. But here was an artifact just waiting to be examined, scrutinized, passed over with a fine-toothed comb. And it wasn’t even on the bottom of the ocean floor like most of the wrecks Delgado had experience working with.

Delgado making notes in the conning tower of the Explorer. Photo courtesy of Sven Robel.
Delgado making notes in the conning tower of the Explorer. Photo courtesy of Sven Robel

Once the team got inside the wreck they began discovering exactly how the sub worked. They found that the upper portion of the sub’s hull was manufactured from pressure-resistant cast iron. And in the fine layer of sand covering the floor, Delgado recovered a depth gauge filled with mercury and the wooden handle of a manual pump, which had evidently been used to improve the air quality in the small, enclosed chamber. Dispersing a mist of fine water vapor was meant to bind the carbon dioxide in the air to help the crew members breathe as they carried out their work by candlelight on the ocean floor. These discoveries closely matched what had been written about the Explorer.

In the summer of 1869, the Mercantile Chronicle, a Panamanian newspaper, went into detail about how the submarine actually functioned. “Before submersion, enough air is filled into the compressed air chamber, using a pump with the power of thirty horses mounted on another boat, until the air in the chamber reaches a density of more than sixty pounds. Once the compressed air tank has been sealed, the men enter the machine through the tower on the upper side and as soon as the water is permitted to fill the ballast chambers, the machine sinks directly down to the ocean floor, where a sufficient amount of compressed air is promptly fed into the working chamber until it possesses sufficient volume and power to resist the enormous pressure of the water, so that the men can open the hatches in the floor of the machine and begin recovering oysters. When they have been underwater for a sufficient period of time and all shells within reach have been collected.” The writer continued, “compressed air is pumped into the ballast chamber and as this air then forces out the water, the machine safely rises to the surface.”

Julius Kroehl and his Pacific Pearl Company crew spent a few months testing the Explorer, diving off the coast of San Telmo, near the end of the harvesting season. It was these final test dives in the Pearl Islands that would eventually lead to the brilliant inventor’s death — and also reveal the submarine’s one fatal flaw. At the season’s end, with Kroehl and his crew all painfully ill, they sailed back to the mainland. It was here, in Panama City, that Julius Kroehl died on September 9th, 1867 from “fever”.

The technology Kroehl implemented in the Explorer truly was revolutionary, but the 1867 pearl-harvesting enterprise was as doomed as it was ground-breaking. A physician by the name of Alfonse Jaminet would not publish his crucial findings on decompression sickness for another four years. The doctors in Panama, the crew — even Kroehl himself — had no idea that nitrogen molecules expand into small gas bubbles in the body when a diver surfaces too rapidly, essentially causing the blood to foam. Kroehl was buried in the Cementerio de Extranjeros(Foreigner’s Cemetery), located in the now dilapidated district of El Chorrillo in Panama City.

In 1869, the Pacific Pearl Company resumed work, this time with Henry A. Dingee in charge of the operation. In September of that year, the company reported a harvest of pearls and pearl shells. The New York Times reported that the Explorer remained “under water four hours, at a depth of 103 feet when it rose to the surface with 1,800 oysters, or about seven-eighths of a ton of shell. The machine afterward made one downward trip each day for eleven days, at the end of which all the men were again down with fever; and it being impossible to continue working with the same men for some time, it was decided, the experiment having proved a complete success, to lay the machine up in an adjacent cove and to convey to the Company the gratifying intelligence. We understand Mr. Dingee proceeded to New York on the 31st with the proceeds of the experimental trial — some ten and a half tons of pearl shells and pearls to the value of $2,000, more or less.” This New York Times article confirms that, even after Kroehl’s death, the crewmembers of the Explorer were still suffering from decompression sickness, or “The Bends” as it’s often called. Delgado asserts “not one in a hundred individuals could avoid decompression sickness in such a circumstance.”

Shortly after, The Philadelphia Inquirer reported, “What has become of the Pacific Pearl Company? Their little submarine boat, which cost one way or another nearly one hundred thousand dollars, has been lying neglected on the sand beach at one of the islands in the Bay of Panama for almost a year past. When its unfortunate builder, Mr. Kroehl, was alive there was a fair prospect of its being a success if funds had been supplied to him to work it, but now it looks as if the boat was entirely abandoned, or if it is not it will very soon, if not already, prove entirely useless.” On April 2, 1924, the Pacific Pearl Company was involuntarily dissolved.

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Delgado, now Director of the Maritime Heritage Program at the National Oceanic and Atmospheric Administration, filed a thirty-seven page report in 2007 with the Panamanian Government urging authorities to recover, preserve and even publicly display the Explorer. “The challenge now before the Sub Marine Explorer is one of conservation, preservation and additional documentation,” Delgado noted in the report. “The exterior of the submarine is actively corroding, and through the action of the surf, and perhaps human intervention, is de-concreted, accelerating the deterioration of the craft’s outer shell. The inflow of water also washes in sand, cobble and some larger rocks. This batters at the edges of the iron and continues to break it. This wreck is not in a stable environment. It is a unique and significant craft in danger.” In the document, Delgado and his team outline the many preservation options available to the Panamanian government—ranging from short term, low-cost remedial efforts like welding braces on the hull’s weaker sections to more expensive, long-term efforts such as raising and transporting the vessel to a desalination tank in Panama City. So far, Panama has done nothing to safeguard theExplorer’s uncertain future aside from an intermittent security presence to protect the wreck from unscrupulous scrap metal scavengers.

It’s impossible to separate this cluster of castaway islands from their rich pearl fishing history. Even the names of islands reveal an entangled story of piracy and commerce. The main island which serves as a hub for the area, Contadora (which means, “bookkeeper” in Spanish), was used by the Spanish conquistadors as a stop for taking inventory of pearls and treasure prior to returning to Spain. Leaving the Explorer’s resting place on Isla San Telmo and heading north through the scattered masses of the archipelago, there is Isla Casaya and its sister island, the smaller, crab-shaped Isla Casayeta — two islands populated mainly by pearl diving villagers who, to this very day, find pearls tucked cozily inside the watery beige flesh of black-lipped oysters on the ocean floor.

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