Bodies of water have always presented challenges to engineers. In the early days, rivers were powerful avenues of commerce. Sooner or later, though, people just wanted to get to the other side of them.

Boats, such as ferries, were the earliest and most obvious solutions. Eventually, engineers began to build bridges. Soon, though, there were people that wanted to tunnel under bodies of water. Other than hiring a crack team of moles and beavers, how could this be done?

As early as 1818, a French engineer named Marc Brunel invented a device that allowed workers to tunnel under rivers without worrying about water and mud ruining their work. Brunel’s “tunnel shield” was a big rectangular iron wall with lots of small shutters in it.

Workers would open the shutters one at a time to dig out a few inches of dirt. After a bit of progress was made, the whole shield would be pushed forward. As the shield advanced a few inches at a time, workers would build a thick brick wall behind it that would become the shell of the tunnel.

This was very time-consuming work, of course. For example, it took workers nine years (from 1825 to 1843) to build a 1,200-foot tunnel below the Thames River in London. This became the first underwater tunnel in the world.

Technology has advanced a lot since Brunel’s day. Today, underwater tunnels are often created with humongous tunnel-boring machines (TBMs) — sometimes called moles. These machines cost millions of dollars, but they can create large tunnels in a very short time.

A circular plate with disk cutters rotates to cut through rock as the machine inches forward slowly. As the machine excavates the tunnel, it also helps to build the walls that will eventually support the tunnel.

France and England used 11 massive TBMs to create — in just three short years — the three tubes that make up the 32-mile Channel Tunnel. Also called the Euro Tunnel or Chunnel, these tunnels now connect the two countries under the English Channel.

Another new method of creating underwater tunnels is the cut-and-cover method. To use this method, builders dig a trench in the riverbed or ocean floor. They then sink pre-made steel or concrete tubes in the trench. After the tubes are covered with a thick layer of rock, workers connect the sections of tubes and pump out any remaining water.

This method was used to create the Ted Williams Tunnel, which connects the southern part of Boston with Logan Airport. The 12 giant steel tubes that were sunk in the trench were each 325 feet long and already contained fully-constructed roads!

Engineers are always coming up with new ideas. Based upon experimental rock-cutting methods, tomorrow’s underwater tunnels might be built with the help of high-pressure water jets, lasers or ultrasonic sound machines.

New technologies could enable the building of tunnels that once seemed impossible. For example, some engineers would like to build a Transatlantic Tunnel to connect New York with London. The 3,100-mile tunnel could house a train that could travel 5,000 miles per hour. The trip that now takes 7 hours by plane could someday take less than one hour!

48 Join the Discussion

1 Star2 Stars3 Stars4 Stars5 Stars  (64 votes, avg. 4.20 out of 5)
    • We’re really happy that you visit Wonderopolis every day, Sera! Thank you so much for telling us! We like that you used context clues to try and guess what tomorrow’s Wonder might be about. We can’t wait to see if your were correct! :-)

    • Hi, Natalia! Thank you for telling us what you thought about this Wonder of the Day®! We think it must be super cool to travel in your car from one side of a body of water to the other…UNDER the WATER! We’re glad you stopped by Wonderopolis today! :-)

    • What a super question, Kate! There are underwater tunnels all over the United States and the world! A few examples found in this Wonder of the Day® are: the Holland Tunnel between New Jersey and New York City, the Ted Williams Tunnel (which connects the southern part of Boston with Logan Airport), and the 32-mile Channel Tunnel which connects France and England under the English Channel! Thanks for hanging out in Wonderopolis and leaving us a comment today! :-)

  1. Really Cool!

    But will tomorrow’s Wonder be better?

    Will it be about those people who take care of plants? What are they called? I know it starts with a B, but I can’t remember. Can you tell me? Thanks! :]

    • Hello, Ninja Girl=]! Are you talking about BOTANISTS? They are special scientists who study plants. Thanks for leaving us another awesome comment today! :-)

    • That sounds like FUN, Luna! Thanks telling us what you thought about today’s Wonder of the Day®! Please let us know when you get to visit an underwater tunnel and share with us what it was like to travel through one, OK? :-)

    • Awww, we love our Wonder Friends, too, MissGirlyGirl21! Thank you for leaving us this cool comment and for letting us know what you think tomorrow’s Wonder will be about. We’ll all have to check back to see if you were right! :-)

    • We’re glad you stopped by Wonderopolis today and learned something new, Zion! Thanks for leaving us this comment to let us know what you thought about this Wonder! :-)

  2. It would be cool if they used it to make a giant tunnel under the ocean to go all the way to Asia, China, Germany, etc., but the down side to that is, if the tunnel were to collapse there woudn’t be any survivors, since the whole place would flood and also the crumbling rock.

    • What a creative way to think about underwater tunnels, Clayton! Maybe someday technology will advance far enough that an underwater tunnel from one continent to another will be a possibility! We’re sure glad you visited this Wonder of the Day® and left us this AWESOME comment! :-)

    • That WOULD be really cool, Jordan! Then, people who have a fear of flying or being on boats would have another way to travel and see the world! What a creative way of thinking…thank you for sharing your idea with your friends in Wonderopolis today! :-)

  3. I have always wanted to go through an underwater tunnel, and I actually wish there was an underwater roller coaster, too. I wonder if that’s possible?

    • We don’t know if it’s possible, Mira, but it sure sounds like a lot of fun! We appreciate your WONDERful imagination! Thank you for sharing your comment with us today! :-)

    • Hi, Amber! It used to take many years to create an underwater tunnel. It took nine years to build a 1,200-foot tunnel below the Thames River in London back in the early 1800’s. With advances in technology, it can now take as little as three years to create one! :-)

    • Welcome to Wonderopolis, Laura and class! Thanks so much for letting us know what you thought about this Wonder of the Day® featuring underwater tunnels! We really like hearing from our Wonder Friends and are super glad you left us a comment today! :-)

  4. I think this one was awesome!!!!!!!!!!!!!!!!!!!! It is really cool to know that this takes a long time to do. I never knew there was the Three Gorges Dam in China!!!!! Well, thanks for all the WONDERS.

    • It makes us super happy to hear that you thought this Wonder was cool and that you learned some interesting new facts about underwater tunnels by exploring it today, Will! Thanks for visiting Wonderopolis! :-)

    • We think it would be cool to visit an underground tunnel, too, Squary11! We WONDER what it would look like under there? Thanks for hanging out in Wonderopolis with us today! :-)

  5. I have to write reports on 5 wonderopolis wonders per week, reading the wonders are really fun I can’t say the same about writing it!!!!!

    • Hi there, John! We think it’s so cool that you are WONDERing with us for homework credit! It sounds like a ton of fun! Good luck writing– we think you’ll do a SUPER job! :)

  6. I love that they took the time to do that and I think it’s crazy how that machine is so big I hope I can drive in an under water tunnel soon.

    • Thanks for sharing your comment, Katie! We’re thrilled that you have been WONDERing about underwater tunnels with us today– we hope you can experience one for yourself soon! Have a marvelous Monday! :)

  7. I think tomorrow’s wonder will be about mountains. This WONDER was pretty outstanding. But I still can’t imagine how people think of these ideas!

    • Thanks for letting us know you thought this WONDER was OUTSTANDING, Morgan! We think you’re pretty OUTSTANDING yourself for spending time WONDERing with us! We have lots of curious Wonder Friends that help us think of some pretty COOL Wonders! :)

  8. The video was very cool. I never knew you could travel under water in a tunnel. It was a hard thing to build. The workers had to be brave because they had to go under water and build. It had to be dangerous! I hope they do build a tunnel to New York to England! I would travel on it!

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Have you ever wondered…

  • How do you build a tunnel underwater?
  • What is a tunnel-boring machine?
  • How will underwater tunnels be built in the future?

Wonder Gallery

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Try It Out

Think you might want to be an engineer who builds amazing underwater tunnels in the future? Keep the learning going by exploring one or more of the following fun activities with a friend or family member:

  • Take some time to imagine what kinds of incredible underwater tunnels could be built in the future. Can you imagine an underwater tunnel connecting New York City with Paris, France? How long would such a tunnel have to be? Look it up on a map or do some Internet research to find out how far it is from New York City to Paris. How much money do you think such a tunnel would cost? Would it be worth it? Would people really be willing to drive under the Atlantic Ocean rather than sailing or flying across it? Why or why not? Would you?
  • Ready to be amazed? Underwater tunnels are only some of the incredible engineering feats that have been accomplished. Check out the links below to explore some of the most amazing projects featuring cutting-edge engineering and technology:
  • Underwater tunnels require engineering skills that push the envelope of modern technology. Do you think you would like to be an engineer someday? There’s one way you could find out. Do some research on engineers and what they do. There are many different types of engineers. Are there any types of engineers that you find intriguing? Do you know any engineers? Perhaps there is an engineering firm in your city or town? If so, contact them to find out if you could meet with an engineer for a few minutes to learn more about what they do. You never know. You might be able to job shadow an engineer for a day. Wouldn’t it be cool to go to a job site to see firsthand what engineers do?

Still Wondering

Check out National Geographic Xpeditions’ Wonderworld lesson to take the challenge to design a theme park devoted to great moments in architecture and engineering.


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