This site is not affiliated with the Discovery Channel or MythBusters. Please visit the Official MythBusters site for official content.

Episode 72: Underwater Car and Seven Folds

  • Seven folds: you can't fold a piece of paper more than seven times: busted
  • Underwater car escape:
    • If a car goes underwater, you cannot open the door until the cabin of the car completely fills with water: confirmed
    • Variations on escape: opening the door when the water is above the...
      • ankles: confirmed
      • knees/waist: confirmed
      • top of window: busted
    • Escaping through the car window: confirmed
      • Opening a car window underwater (before the pressure equalizes):
      • manually powered window: busted
      • electrically powered window: busted -- though an electrical window does operate underwater
      • Breaking a car window underwater with:
      • keys: busted
      • cellphone: busted
      • steel toed boots: busted
      • emergency window hammer: confirmed
      • spring-loaded window punch: confirmed
    • Escaping by waiting (holding breath until pressure equalizes): confirmed

Underwater Car Escape is one of those rare myths that you can apply in real life. Adam and Jamie relentlessly tested this myth and showed viewers the opportune moments for escaping from a car slipping underwater. I wouldn't be surprised if sales of emergency hammers and spring-loaded window punches increases after this episode.

The Seven Folds myth was a fun experiment culminating in the folding of a gigantic 170' x 220' piece of a paper.

Underwater Car Escape

Myth: If a car goes underwater, you cannot open the door until the cabin of the car completely fills with water

In 2005 (2006?), AAA estimate 11,000 vehicles went into the water. 300 people died as a result.

Small-scale test

Filled a 3' deep cylinder with water. Adam lowered a plastic box to represent a car into the tank. He also rigged up some drums to measure the relative air pressure. Adam's rig showed that the pressure outside was initially greater, but eventually equalizes.


  • Pool, 13ft deep (Compolidno High School)
  • Car: they crudely removed the engine from the car to prevent engine fluids from leaking into the pool. The engine was replaced with an equivalent amount of weight.
  • Adam was chosen as the driver while Jamie sat in the back seat wearing a rebreather. There was also an emergency tank of air for Adam.

Jamie: "Adam, I only have one thing to say to you: don't pee in the pool."

First test

The car was lowered into the pool. As soon as Adam was fully under, he started to try and open the car door. He wasn't able to get the door to budge. He was able to finally open it when the car cabin completely filled and the car started to level out, but not until after he had to get the emergency air from Jamie. It was 1:51 from the time the water hit Adam's knees until he surfaced.

Adam: "That is intense, no matter how you slice it. I died. Let's just put it that way."

Jamie: "Well, you died."

Second, third, and fourth test

Clearly, waiting until the water was above his head was too late to open the door. They repeated the initial test, but varied when Adam first tried to open the door: * Ankles: Adam tried to open the door as soon as the water hit his ankles. It took some effort, but he was able to open it. confirmed * Knees/waist: Adam waited until the water hit his knees to start opening the door. It took almost all of Adam's strength, but he was able to escape. confirmed * Top of window: As soon as the water hit the top of the window, Adam started pushing. There wasn't even the slightest budge in the door. busted

Opening the window underwater

Instead of opening the door while underwater, they also wanted to test opening the window underwater before the pressure equalized.

  • Manual powered window: Adam stuck 350lbs of weight on top of a manual powered window. The manual crank failed as Adam attempted to open the window. busted
  • Electrically powered window: They stuck an electrically powered window underwater and showed that it could continue to operate even a full hour after it was submerged. This took care of the first requirement, but, as soon as Adam stuck 350lbs of weight on top of it, the results were no better than the manual window. busted

Breaking the window

Adam and Jamie tested various objects that you might have in a car to break through the window.

  • keys: busted
  • cellphone: busted
  • steel toed boots: Adam kicked the window repeatedly underwater but wasn't able to break through. busted
  • emergency window hammer: the commercial solution shattered the window with a single hit. confirmed
  • spring-loaded window punch: this commercial tool also made quick work of the window. confirmed

Escaping through the window

They couldn't break the window underwater due to the location they were testing out (no broken glass allowed). Instead, they rigged up the window with lubricant and a high-speed trigger. Adam waited until the water almost reached the top of the window before triggering the electrical windows. The water came pouring it but Adam was able to easily escape.


Escaping by waiting

Instead of expending all of his effort trying to open the door when the pressure was too great, Jamie recommended that Adam stay calm, hold his breath, and wait until the pressure equalized. It took 1:37, but Adam was able to wait it out and open the door.


Seven Folds

Myth: You can't fold a piece of a paper in half more than seven times (the 'traditional' way)

This myth was qualified that the spirit of the of the myth was that you had to alternate folding directions each time you folded it in half.

Exponential growth: A piece of paper folded 7 times has 128 layers, 8 times has 256 layers.

In 2002, Britney Gallivan got more than seven folds by folding toilet paper over 4000' long. It took seven hours in a shopping mall, but Brtiney was able to achieve 12 folds and also derive an equation relating the width and thickness of a paper to the number of folds achievable.

Build team challenge

Each build team member was given 2 hours to fold a piece of a paper as many times as possible:

  • Tory folded and massaged a standard piece of 8 1/2" x 11" paper seven times. For the eighth fold, he ended up wrenching it over into a wad.
  • Kari used an iron and sandpaper to try and get each fold as tight as possible. Kari was also stuck at seven
  • Grant went with thinner paper. The office paper that Tory and Kari were using was .003" thick. Grant went with thinner tracing paper and also used a different folding strategy. He folded lengthwise first and then switched to width-wise for the final folds. Grant as able to achieve eight folds using this technique.

A bigger piece of paper

They rolled out a 12.5' x 15' sheet of paper and used a heavy roller to compress each fold. They still couldn't break seven folds using the 'traditional' technique.

An even bigger piece of paper

A single roll of paper wasn't bit enough, so they decided to make their open big 170' x 220' piece using 17 rolls of paper joined together with double-sided tape. An experiment this large required that they go to Moffett Field and setup in one of the blimp hangers there.

Using the traditional technique of alternating folds length and width-wise, they were able to get eleven folds. They were able to get eight folds using their team of people. For the final three rolls, they had to roll in the industrial help: a Dynapac roller and a forklift.



Does an emergency hammer work when the cabin is full of water?

Does any hand held emergency tool that relies on physical movement work when the cabin is full, for that matter?

the name of the school pool was misspelled.
Campolindo High School
Moraga, CA