To Defeat the Royal Navy During the American Revolution, a Rebel Inventor Designed a Secret Weapon: a Bomb-Carrying Submarine

David Bushnell developed the “Turtle” submersible as a student at Yale University. The vessel’s attack on a British flagship failed, but the trailblazing boat’s legacy endures 250 years later

Eliza McGraw | History Correspondent

September 3, 2026 7:45 a.m.

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During the American Revolution, the Turtle made history as the world’s first combat-ready submarine. If all went according to plan, the driver of the acorn-shaped submersible—constructed out of oak and iron hoops—would descend, draw close enough to a warship to attach a bomb to its hull and then make their escape by ascending to the surface.

Connecticut inventor David Bushnell designed the Turtle as a secret weapon for the patriots to wield against the British. Nearly 250 years ago, on the night of September 6-7, 1776, the vessel targeted the Royal Navy’s flagship, the HMS Eagle—and failed. In the centuries since, however, the story of the souped-up submersible that went up against the greatest navy in the world has served as a testament to the revolutionary spirit.

Bushnell started experimenting with gunpowder while enrolled at Yale University in New Haven, Connecticut. He knew that a bomb affixed to a ship’s hull would inflict more damage than one placed on its deck. First, he had to figure out how to get explosives to work underwater. Then he would turn to the question of how to transport the device.

As early as 1771, students at Yale had gathered at a local pub to debate how to defeat the Royal Navy in “the inevitable war with Britain,” says Mark Jacobson, a historian at the International Spy Museum in Washington, D.C. “They understood limiting the capability of the Royal Navy was key, but that you couldn’t take them on head-on.”

Bushnell’s solution to this problem was a propeller-driven submersible. To bring his vision to life, the inventor worked with his brother Ezra Bushnell, as well as his teachers, mentors and colleagues at Yale.

“Ideas led to designs that were then produced, installed, tested and modified as necessary,” authors Roy R. Manstan and Frederic J. Frese write in Turtle: David Bushnell’s Revolutionary Vessel. “It was a four-year process involving the unique talents of many individuals.” Local clockmaker Isaac Doolittle, for example, helped create the timing mechanism for the bomb, as well as the Turtle’s valves and pumps.

By the time the Revolution began in the spring of 1775, Bushnell had nearly finished the hull of his invention. Regarding the submersible’s name, the inventor later told Thomas Jefferson that “the external shape of the submarine vessel bore some resemblance to two upper tortoise shells of equal size, joined together, the place of entrance into the vessel being represented by the opening made by the swell of the shells, at the head of the animal.”

The Turtle could hold just one person at a time. After climbing into the vessel, the pilot would use a pedal-operated front propeller and a hand crank to move, submerging only upon nearing the enemy ship. To descend, they would fill the central chamber with water by opening a valve, leaving just enough room to breathe at the top.

Small windows let in light, and the bent snorkel shape of the air vents prevented water from seeping in while the Turtle was submerged. Inside, the barometer and compass were coated with a bioluminescent fungus called foxfire so the pilot could make them out in the dark. (Unfortunately, this fungus only produced light above a certain temperature, making it impossible for the patriots to use the Turtle in the winter.)

A “large powder magazine” designed to be screwed onto an enemy ship’s hull rested above the submarine’s rudder, equipped with a timer that would allow the pilot to set off the bomb at “any proposed length of time under 12 hours,” as Bushnell later told Jefferson. The apparatus that triggered the bomb “could not possibly move till, by casting off the magazine from the vessel, it was set in motion,” the inventor added.

To ascend after placing the explosive, the vessel’s operator used bilge pumps to remove water from the chamber. The individual needed strength to pump those bilges and faith that they would work. Breathing hard while pumping, pedaling and attaching a bomb required plenty of oxygen, and pilots knew that they were working on a tight deadline. As George Washington wrote to Jefferson in 1785, “It is no easy matter to get a person hardy enough to encounter the variety of dangers to which he must be exposed.”

Meet the First Submarine Used in Combat

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Originally, the Turtle was supposed to attack British ships in Boston. By the time the craft and crew were ready for action, however, the British had moved their ships to New York City. The Turtle followed, reportedly transported from Connecticut to New York aboard a small sloop. Before the submarine could mount its attack, however, its operator, Bushnell’s brother Ezra, fell sick. A replacement pilot, Ezra Lee, set out for the British flagship, the Eagle, around midnight on September 6, 1776.

Lee piloted the Turtle to the Eagle but couldn’t fasten the charge to its metal hull. “When I rowed under the stern of the ship,” he later wrote, “[I] could see the men on deck and hear them talk—I then shut down all the doors, sunk down and came under the bottom of the ship, up with the screw against the bottom, but found that it would not enter.” Lee fled, leaving the charge behind. It exploded in the harbor but didn’t damage the Eagle, although the commotion did surprise nearby ships.

In the weeks that followed, two subsequent attempts—one by Lee and the other by pilot Phineas Pratt—similarly failed. As for the Turtle itself, the submarine’s fate is unknown. The British sank the sloop transporting the vessel in October 1776, but Bushnell claimed that he’d salvaged the submersible and brought it back home. Pratt’s son later said that he’d seen disassembled components of the Turtle as a teenager in 1800.

Why isn’t the Turtle more famous today? Evan Wilson, a historian at the U.S. Naval War College’s Hattendorf Historical Center, offers several reasons. “First, all of Turtle’s attacks failed, and second, the launching of Turtle did not herald the age of the submarine—that was still more than a hundred years away,” he says. “A wooden-hulled submersible carrying one person was never likely to be the foundation for a new era of naval warfare.”

In the centuries since the submersible’s failed attacks, the “undersea domain has become essential to naval warfare,” Wilson says. “Turtle is the earliest indication of the possibilities of that domain, but the metallurgical and propulsive technologies necessary to operate underwater were still a long way off.”

Together with the Nautilus, a hand-propelled submarine designed by American Robert Fulton in 1800, Bushnell’s Turtle shows that “innovators were starting to think seriously about the possibilities of submersibles in the Revolutionary era, even if they couldn’t make what we would identify as a true submarine” that can operate independently underwater, Wilson explains. “Submersibles usually need to be carried to the place they’re operating,” he adds, and they may require support from ship or shore.

Jacobson draws a direct line between early combat submarines and 20th-century innovations. “The possibility of swimmers and divers being armed with underwater timed explosive devices will eventually evolve into the frogmen of World War II” (scouts who swam onto enemy beaches to clear obstacles ahead of amphibious invasions) and the Navy SEALs, he says. The Turtle’s oar-like propellers, meanwhile, were the first of their kind to be used in a maritime vessel for propulsion, paving the way for the screw propellers popularized in the 19th century.

“Military and naval historians think about the Turtle as an asymmetric weapon,” Wilson says. “In other words, it was very difficult—probably impossible—for the American rebels to challenge the British Navy symmetrically, by building their own navy.”

The Continental Navy simply couldn’t control the seaboard from South Carolina to Massachusetts. “The promise of the Turtle was that it would be able to sink a British 64-gun ship that carried at least 500 men, and it would also cause the British to worry that all of their ships were vulnerable while at anchor off the American coast,” Wilson explains. “Even better, the Turtle itself cost very little and had just one operator. If it had worked, it would have been a classic example of an insurgency using asymmetric warfare to its advantage.”

On that crucial night in 1776, the Turtle failed to blow up an enemy warship. Despite this, Bushnell’s contemporaries knew that the vessel was something special. Before his death in 1826, the inventor developed a torpedo that could be transported behind a whaleboat, and he worked on designs for other underwater mines. “Bushnell is a man of great mechanical powers—fertile of invention—and a master in execution,” Washington wrote in 1785. “I then thought, and still think, that it was an effort of genius.”

Eliza McGraw is the author of Here Comes Exterminator!, a book about the 1918 Kentucky Derby winner. She lives in Washington, D.C.