Name: The World’s First Combat Submarine
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During the American Revolution, an American inventor developed an underwater vessel that could destroy British ships by attaching a bomb to the hull of a ship. These are some of its unique features.

The World’s First Combat Submarine

World’s First Combat Submarine

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During the American Revolution, an American inventor developed an underwater vessel that could destroy British ships by attaching a bomb to the hull of a ship. These are some of its unique features.

Its nickname was the “Turtle”.

Military & Espionage

The World’s First Combat SubmarinePublished: April 17, 2025MIKE LOADES: This is a model of the first combat submarine. Now I say model because the original doesn't exist. All we have is a few hints and clues from subsequent writings.NARRATOR: The writings come from American inventor David Bushnell.DAVID BUSHNELL: The external shape of the submarine vessel bore some resemblance to two upper tortoise shells of equal size, joined together.NARRATOR: It was later nicknamed the Turtle.MIKE LOADES: First, you've got the overall shape. It's using the technology of a barrel. It's thick oak staves, bound together with iron hoops. It's not quite barrel shaped though. And the reason for that is because you need space inside for an operator to sit. So that's going to broaden it in the middle. And you need space at the top for a hatch for the operator to get in.At first glance, it immediately reminds you of a space capsule. But what it is, in fact, is a time capsule, a time capsule of contemporary technologies. You've got these pedals here, so the operator is pedaling away. This is powered by pedal power, and they are driving a propeller.NARRATOR: The concept of the propeller dates back to Greek mathematician Archimedes. His Archimedes screw famously moved water using a spiral blade inside a tube. Bushnell took this concept and located a blade on the outside of his turtle. This is thought to be one of the first practical applications of a propeller, along with a rudder. The turtle has all the components needed to maneuver on the surface.MIKE LOADES: A particular feature on the outside of the vessel is this hatch at the top here. It's got these water tight windows, so he has got some natural light inside. Then above that, these strange looking things are really snorkels, so that when it's above water, it's fully ventilated.NARRATOR: Using the windows, the operator could maneuver on the surface to locate and position the turtle next to a ship. It is then ready to descend by filling the area at the base of the vessel, known as the bilges. To do that, the operator kicks a lever.MIKE LOADES: This will flood the bilges down there with water.NARRATOR: Under the surface, a second propeller is used to lower or raise the turtle. Once submerged in darkness, the operator has only two instruments for guidanceMIKE LOADES: This is a barometer. It has a little cork in it, and each of these marks on the glass tube represents a fathom that's about six feet. So as he sees the cork bobbing down, he knows he's going down another six feet. How can you see that underwater? Because it's been covered with a fungus called foxfire, which is luminous, it glows in the dark.And over here is a compass, which again, the needle on the compass has been coated with this luminous fungus so he can read his heading.NARRATOR: The turtle is designed to move into position. Armed with a bomb to blow up its target.MIKE LOADES: So, assuming that we've now got to the right that we now need to attach the payload. And that's this crank here, this crank operates that drill at the top and that bores its way up into the hull of a ship.NARRATOR: The drill is attached to the bomb by a rope. Once connected, the turtle detaches itself, leaving the explosives secured to the ship.MIKE LOADES: And now you've got to get out of here. So you you pedal away when you want to surface, you use these two hand pumps, yet more exertion to save your life. Pumping away to get that water out of the bilges. But my goodness, that's a heck of a lot of work to get to that stage.NARRATOR: Employed to carry out this dangerous mission, 27 year old American Ezra Lee. The plan: drive into New York Harbor and blow up the British flagship HMS Eagle. But how could Ezra Lee attach a bomb big enough to sink the British ship and get away safely? Inventor David Bushnell's writings provide some clues, allowing pyrotechnics expert John Hargreaves to figure out how it was supposed to happen.JOHN HARGREAVES: I've rigged this as a demonstration. This is pretty much the size of the bomb that would have been on the turtle.MIKE LOADES: That holds the gunpowder?JOHN HARGREAVES: Correct, 150 pounds.MIKE LOADES: How do we get a spark to it?JOHN HARGREAVES: Well, in the references to Bushnell's machine, they show a flintlock mechanism.MIKE LOADES: So this little pocket pistol?JOHN HARGREAVES: Correct.MIKE LOADES: Which has got this flint lock here so that flint strikes that which creates the spark.NARRATOR: The pistols’ muzzle is screwed into the barrel. When it's fired, it will ignite the gunpowder. But Ezra Lee would need time to escape before it exploded. Bushnell had a plan.DAVID BUSHNELL: Within the magazine was an apparatus constructed to run any proposed length of time under 12 hours.JOHN HARGREAVES: This is a specialist clock. It is a very early 19th century version, actually, but it is the nearest thing I can find to the right mechanism.NARRATOR: The mechanism John thinks Bushnell used comes from a period pocket watch.JOHN HARGREAVES: The pocket watch had been around the beginning of the 17th century. It was a pretty rare thing. And they were all watches like this. The clock is going to count down to zero when it gets to zero. It pulls a lever which I have attached to the trigger mechanism of my pistol, so it pulls the trigger and fires the gun.MIKE LOADES: This is absolutely ingenious, John.JOHN HARGREAVES: I'm going to set it to a minute to. Can you hear it ticking?MIKE LOADES: We have a ticking bomb.JOHN HARGREAVES: This is ticking.MIKE LOADES: Oh, look at that. Excellent. Proof of concept.JOHN HARGREAVES: Yes.NARRATOR: The timer for the bomb was set to 30 minutes and sealed in a watertight casing. The countdown would begin when the bomb detached from the turtle.DAVID BUSHNELL: This apparatus could not possibly move till by casting off the magazine from the vessel it was set in motion.NARRATOR: The firing mechanism works on land. But will the bomb explode underwater? When Bushnell first tested the bomb, he did so with varying amounts of gunpowder. For safety, John is only using 5 pounds. Ezra Lee was carrying 150.At 11 p.m. on September 6th, 1776, after being launched into the water from a whale boat, Lee starts his mission.Even though this was a scaled down test. John is taking all the necessary precautions. As Raleigh is facing the real risk that the bomb could fail to detonate or worse, explode too early, killing him instantly. For over two exhausting hours, with the constant risk of being spotted, he navigates toward the British ship. Upon reaching it, he begins his descent, dropping close to 30ft below the surface with the bomb.MIKE LOADES: Oh! Yeah, she blows.That's just 5 pounds?JOHN HARGREAVES: Yes, 5 pounds of gunpowder.MIKE LOADES: The bomb they're dealing with was 30 times that magnitude.NARRATOR: A detonation that large would have been catastrophic. The wooden hull of a ship offers less resistance to the bomb's explosive force. And the denser water around it.MIKE LOADES: It would have just ripped through the bottom of the boat. Instant destruction in.NARRATOR: But HMS Eagle is not blown up. After making his descent as Ezra Lee is unable to attach the bomb.DAVID BUSHNELL: He went under the ship and attempted to fix the wooden screw, but struck, as he supposes, a bar of iron.NARRATOR: At this crucial moment, running out of air, he abandons the mission. In a later attempt, the boat carrying the sub is sunk by British gunfire. This is the end of the turtle.MIKE LOADES: I have absolutely no doubt that if it had been successful and if it had been repeatable to scale, if they built many more turtles and they had destroyed the British fleet, it would have shortened the war by years. The war would have been over in months.

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The World’s First Combat Submarine

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Support Provided By

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