The submarine created by inventor Julius Hermann Kroehl made pearl diving less labor-intensive but also led to the deaths of many divers.
In 1863, German-American inventor and engineer Julius Hermann Kroehl founded the Pacific Pearl Company with the aim of profiting from pearls in the region’s waters. To alleviate the laborious process of pearl diving, he began constructing a submarine specially designed to assist in the collection of oysters and clams, according to Amusing Planet.
Pearl diving relied entirely on divers working without breathing apparatus. These divers would descend to depths of 6 to 12 meters, collecting as many shells as possible before surfacing, often holding their breath for up to a minute. The work took place during low tide, allowing access to deeper areas of the seabed. However, the diving time was very short, lasting only 2 to 3 hours. Within this limited timeframe, divers would make 12 to 15 dives to the seabed. Aware of the risks and inefficiencies of this method, Kroehl sought a solution to revolutionize the process, helping divers avoid unnecessary dangers while improving productivity.
The wreck of the Sub Marine Explorer in 2006. (Image: James P. Delgado).
The Sub Marine Explorer designed by Kroehl was 11 meters long and had a diameter of 3 meters, weighing 80 tons. The complex design included three separate sections: a pressurized air chamber beneath the upper hull, a working chamber in the center for the crew, and a series of 10 ballast tanks. To dive, a steam-powered supply vessel would pump high-pressure air into the air chamber, compressing it to 13.6 atmospheres. Once the chamber was filled, Kroehl and his team would open the valves from the central control station and flood the ballast tanks to submerge the submarine. As water flowed in, the air it displaced would travel through a series of discharge pipes to the distribution pipe, which then expelled it through a valve in the conning tower. Kroehl navigated the vessel by controlling the flooding water and relied on pressurized air to expel seawater from the ballast tanks.
Once the submarine was underwater, the pressurized air was released into the working chamber until the pressure inside balanced with the surrounding seawater. At this point, the hatch at the bottom of the submarine could be opened without allowing water to enter. Thanks to the air inside the working chamber effectively blocking water, divers could emerge to collect oysters for pearls.
To generate propulsion, the Sub Marine Explorer utilized a hand-cranked propeller capable of reaching speeds of 7.4 km/h. Additionally, the air inside the vessel was refreshed by spraying seawater through a chemical compound, maintaining breathable conditions for extended dives. To surface, more pressurized air was pumped into the ballast tanks to expel the water.
The Sub Marine Explorer successfully completed several dives off the coast of Panama, demonstrating the potential of submarine technology in pearl diving. Notably, on one dive, the crew retrieved 1,800 oysters, weighing nearly 900 kilograms in just four hours. However, after 11 days of searching for oysters, all crew members fell ill with an unknown fever, and some died shortly thereafter. Local accounts suggest that these fatalities occurred after prolonged dives at depths exceeding 30 meters and rapid ascents.
At that time, both Kroehl and the crew did not fully understand that the cause of the tragedy was decompression sickness. This condition results from the physiological effects of breathing pressurized air underwater. When a diver swims down, the surrounding pressure increases, causing gases like nitrogen to dissolve into the blood and tissues. If the diver ascends too quickly, the pressure drops suddenly, leading to the formation of gas bubbles in the body, resulting in various symptoms.
The effects of decompression sickness can vary widely, ranging from mild joint pain and rashes to more severe consequences such as paralysis or even death. Nitrogen bubbles often accumulate in crucial joints like the knees or wrists, forcing victims to bend over in pain. Kroehl and the crew were unaware that they needed to ascend slowly under controlled conditions to avoid life-threatening complications.
Kroehl died in September 1867 from a fever, although there has been speculation that his death was related to decompression sickness from experimental dives with the Sub Marine Explorer. However, his wife dismissed this theory, suggesting he died from malaria contracted during the Vicksburg campaign.
With Kroehl’s leadership and financial resources lacking, the Pacific Pearl Company ceased operations. The crew returned to New York, leaving the Sub Marine Explorer stranded. In 1869, another team refurbished the vessel and brought it back to the Pearl Islands to continue harvesting shells and pearls. However, the deep dives resulted in many divers falling ill or dying. The tragedy repeated itself, forcing them to abandon the vessel in a cave on San Telmo Island.
For decades, the rusty hulk of the ship intrigued local residents. In the early 2000s, James P. Delgado, an archaeologist at the American Maritime Archaeology Institute, rediscovered the 19th-century vessel. Despite the interest in the Sub Marine Explorer, research and recovery efforts faced obstacles due to financial and logistical challenges. As of 2010, the ship remained submerged, its metal shell severely corroded after decades of exposure to seawater. Analyses confirmed that the ship had reached a state of significant deterioration. Without preservation measures, it would decay to an irreparable extent.
