Human fascination extends beyond exploring the space above us; we have always been equally intrigued by the mysterious depths of our vast ocean. Despite venturing into the far reaches of outer space before delving into the vast depths of our own ocean backyard, underwater exploration has achieved significant milestones through the development of functional submersibles. These remarkable vessels have enabled us to uncover the mysteries hidden beneath that dark, inhospitable liquid abyss that blankets our planet.

Throughout history, these silent guardians of the deep have undergone a remarkable evolution, evolving from basic submersible crafts to formidable war machines. In this article, we trace the origins of these vessels, from their seemingly impossible conception to their pivotal role in shaping the history of naval warfare.

Dating Back to da Vinci

Historians suggest that the concept of underwater crafts can be traced back to the late 1400s when the renowned Italian Renaissance artist and inventor Leonardo da Vinci claimed to have discovered a method to submerge a ship for an extended period. However, da Vinci kept his discovery a secret due to fears that it could be misused by assassins, who were prevalent during that time. It is worth noting that even before da Vinci’s undisclosed blueprint for a functional submersible, the idea of utilizing underwater vessels for combat purposes had ancient origins.

The first practical submersible took a couple more centuries to move beyond the conceptual phase and into actual construction. However, despite the potential shown by the leather-covered, 12-oar rowboat, its viability was eventually dismissed by the Royal Navy during the development process.

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A reconstructed model of the Drebbel wooden submarine by British boatbuilder Mark Edwards, 2002. (Image source: Wikimedia Commons)

On the other hand, America built its first military submarine in the mid-18th century, aptly named the Turtle. Designed by inventor David Bushnell, the one-person submersible vessel has a compact structure of about 6 feet (1.8 meters) in length and 3 feet (0.9 meters) in height and was made of wood and metal. It was much like an aquatic bicycle, its propulsion powered by a hand-cranked propeller allowing the craft to move on the surface and underwater. It also featured a ballast tank that could be flooded with water to submerge the vessel or pumped out to resurface.

One of the most distinctive aspects of the Turtle was its attack mechanism—a large screw-like device attached to the front. During operations, the operator would approach the target ship, drill into its hull using the screw, and attach a mine fitted with a timer. Reportedly, the Turtle’s first notable mission occurred in 1776, during the Battle of New York, intending to attack the British warship HMS Eagle. Even though the mission would be unsuccessful, it marked the first use of submarines for combat—and the development just took off from there.

Trial and Error

In the early 19th century, renowned inventor Robert Fulton introduced the Nautilus, a remarkable vessel that is often hailed as the first practical submarine. Although it relied on human power and lacked combat capabilities, similar to the Turtle, the Nautilus laid the groundwork for future advancements in submarine design. Despite being considered experimental and unsafe for combat, submarines of this era played a role in the American Civil War.

Among these experimental underwater crafts was the Confederate H.L. Hunley, named after its primary benefactor Horace L. Hunley. Measuring nearly 40 feet (12 meters) in length, this vessel was operated by a small crew of eight men who used a crank mechanism to propel it forward. Despite its limitations, the H.L. Hunley bravely participated in the chaotic naval warfare against Union forces, exemplifying the pioneering spirit of submarine exploration during that time.

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The wreck of H. L. Hunley was recovered off Charleston Harbor on August 8, 2000. (Image source: Wikimedia Commons)

Despite sinking twice and losing about a dozen crew in training missions, including the financier himself, Hunley achieved a historic feat by attacking and sinking the Union Navy’s USS Housatonic by ramming a spar torpedo into the latter’s hull. Shortly after that successful striking, Hunley mysteriously sank and will never be found again until its discovery on the ocean floor in the late 20th century, with its wreckage recovery occurring in 2000.

Submersing To New Depths

During the two World Wars, submarines emerged as formidable naval warfare instruments with the introduction of diesel-electric propulsion systems. The power plant marked a turning point in its evolution, allowing submarines to operate for extended periods and strike with stealth. During this period, what was once considered an impossible concept became a viable undersea vessel, which eventually played a significant role in naval blockades, disrupting supply chains and challenging the dominance of surface vessels. And it became a menace at sea, with the German U-boats, such as the Type VII and Type IX, demonstrating the submarines’ capabilities by wreaking havoc on Allied shipping, turning the Atlantic into a perilous battleground in the process. Simultaneously, the American Gato and Balao-class submarines spearheaded the Pacific campaign, carrying out daring covert operations and crippling enemy fleets.

Simply put, the technological advancements of the era propelled the platform to new heights, or should I say new depths. Nevertheless, while sensors, including radar and sonar, made significant improvements, the rest of the development remains slow, with submersion time continuing to be limited. The range, however, increased, and also the underwater craft’s size.

With the introduction of nuclear-powered submarines in the 1950s, they were able to reach unprecedented depths, marking the beginning of a major revolution in naval warfare.

The USS Nautilus was the world’s first nuclear-powered submarine, marking a significant milestone in submarine technology and making submersible vessels come true to their name, now able to operate underwater at high speeds for indefinite periods. This breakthrough also elevated the platform’s stealth, endurance, and striking power ability.

From that point forward, submarines achieved one milestone after another. Technological advancements were constantly improving, hull designs became more efficient, and state-of-the-art sonar and weaponry systems were installed, transforming submarines into highly sophisticated military naval assets.

Future Horizons: Unmanned Submersibles and Underwater Drones

From barely viable leather-covered rowboats to nuclear-powered streamlined modern vessels, submarines have made enormous strides since their conception—now boasting advanced stealth features, increased automation, and enhanced communication capabilities, allowing them to gather intelligence, launch precise strikes, and engage in cooperative operations with other naval assets. Furthermore, as technology continues to evolve, unmanned submersibles and underwater drones are becoming more appealing, emerging as the next frontier in submarine warfare. These autonomous vessels possess the potential to conduct covert operations, gather intelligence, and perform various tasks with reduced risk to human personnel. The future of military submarines may one day witness a fusion of manned and unmanned platforms that would further expand underwater warfare’s capabilities and adaptability.

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