What’s It Feel Like To Plunge 6.8 Miles Into the Sea?

Answers to your questions about the news.
March 27 2012 7:03 PM

Why Do Deep-Sea Explorers Wear Those Tiny Knit Caps?

The ins and out of submersible travel.

Jacques Cousteau, James Cameron and Steve Zissou wearing skullcaps.
James Cameron, center, emerges from the Deepsea Challenger submersible after his successful solo dive to the Mariana Trench. The dive was part of Deepsea Challenge, a joint scientific expedition by Cameron, the National Geographic Society, and Rolex. At left, marine explorer Jacques Cousteau. At right, Bill Murray as Steve Zissou in The Life Aquatic.

Office of National Marine Sanctuaries, NOAA; Mark Thiessen/National Geographic; IMDB, © Touchstone Pictures.

Director James Cameron successfully completed a 6.8-mile-deep dive to the most remote region of the ocean Sunday and was shown emerging from his submarine in a small knit cap. Jacques Cousteau’s red knit cap was a signature part of his look, which was aped by Bill Murray and his crew in the movie The Life Aquatic With Steve Zissou. Why do underwater explorers wear skullcaps?

Forrest Wickman Forrest Wickman

Forrest Wickman is a Slate staff writer. 

Because it’s practically freezing down there. The water temperature at the bottom of the ocean usually hovers around 37 degrees Fahrenheit, and most deep-sea exploration vehicles don’t have climate control. Explorers tend to bring hats, gloves, long johns, and other warm layers, which they pull on as they descend and the temperature drops. Socks and caps are particularly important, as it’s coldest on the floor and ceiling of the submersible. Because of concerns over electrical fires, deep-sea explorers wear natural fibers like cotton and especially wool, which is fire retardant, instead of synthetic fabrics.

Deep-sea divers have been wearing skullcaps, also known as watch caps or seaman’s caps, since long before the adventures of Jacques Cousteau. He may have picked up the style from hard-hat divers—those 19th-century explorers who wore big copper helmets—who favored red knit caps for decades. The character of Steve Zissou in The Life Aquatic wore an identical cap in homage to Cousteau.

Aside from the extreme temperature, diving in a deep-sea submersible is much like flying in an airplane, except a much tighter squeeze. In order to withstand the crushing pressure of deep waters, the vehicles must be compact and often have spherical cabins. Changing clothes is difficult because there’s rarely enough room to stand. Going to the bathroom, for which there is little privacy, is a particular challenge for female explorers, who have to contort themselves more than men to use the urine-collection bottles. (The bottles come with different attachments for men and women.) While divers may avoid drinking fluids in order to put off urination, they must also be careful not to become dehydrated. For long dives, air can be recycled using carbon dioxide scrubbers and oxygen generators. (Scientists have attempted to develop liquid breathing, the technology used in Cameron’s deep-sea thriller The Abyss. Just as in the movie, mice were able to adjust to breathing the liquid. However, the application of liquid breathing for human diving remains hypothetical.) Still, these technologies can’t always keep up with passengers’ demand for oxygen, and enough carbon dioxide can accumulate to cause headaches. The cabin is pressurized enough that divers will feel little of the extreme pressure outside of the vehicle—dangers like nitrogen narcosis and the bends aren’t a concern in a functioning vehicle—but their ears might pop when the submarine is opened and repressurizes at the surface.

The prospect of deep diving may seem exciting and include moments of thrilling discoveries, but the trip itself is hardly a thrill ride. Vehicles usually travel at a maximum speed of only 2 or 3 miles per hour, so divers sense little of the motion of ascent and descent. Since it can take several hours to reach the seabed, most of the trip can be spent just passing time. Pilots and solo explorers like Cameron must be mindful throughout the journey, but passengers may simply gaze out the porthole (though the water goes dark after about 10 minutes), read, or doze off; some occupy themselves with a computer or music. When resurfacing, however, turbulent waters around the surface can feel like an amusement park ride, or worse, and many craft don’t have seats or seat belts.

Got a question about today’s news? Ask the Explainer.

Explainer thanks Barbara Campbell and Craig Cary of the University of Delaware.

Video Explainer: Why Aren't There More Slam Dunks in Women's Basketball?

This video was produced from an original Explainer by Brian Palmer. Want more questions answered? You can now watch video Explainers at Slate's News Channel  on YouTube.

TODAY IN SLATE

War Stories

The Right Target

Why Obama’s airstrikes against ISIS may be more effective than people expect.

Why Is This Mother in Prison for Helping Her Daughter Get an Abortion?

The XX Factor
Sept. 23 2014 11:13 AM Why Is This Mother in Prison for Helping Her Daughter Get an Abortion?

Divestment Is Fine but Mostly Symbolic. There’s a Better Way for Universities to Fight Climate Change.

I Stand With Emma Watson on Women’s Rights

Even though I know I’m going to get flak for it.

It Is Very Stupid to Compare Hope Solo to Ray Rice

Building a Better Workplace

In Defense of HR

Startups and small businesses shouldn’t skip over a human resources department.

It’s Legal for Obama to Bomb Syria Because He Says It Is

How Ted Cruz and Scott Brown Misunderstand What It Means to Be an American Citizen

  News & Politics
War Stories
Sept. 23 2014 4:04 PM The Right Target Why Obama’s airstrikes against ISIS may be more effective than people expect.
  Business
Moneybox
Sept. 23 2014 2:08 PM Home Depot’s Former Lead Security Engineer Had a Legacy of Sabotage
  Life
Outward
Sept. 23 2014 1:57 PM Would a Second Sarkozy Presidency End Marriage Equality in France?
  Double X
The XX Factor
Sept. 23 2014 2:32 PM Politico Asks: Why Is Gabby Giffords So “Ruthless” on Gun Control?
  Slate Plus
Political Gabfest
Sept. 23 2014 3:04 PM Chicago Gabfest How to get your tickets before anyone else.
  Arts
Brow Beat
Sept. 23 2014 4:09 PM Vince Vaughn Will Star in True Detective Season 2
  Technology
Future Tense
Sept. 23 2014 1:50 PM Oh, the Futility! Frogs Try to Catch Worms off of an iPhone Video.
  Health & Science
Science
Sept. 23 2014 1:38 PM Why Is Fall Red in America but Yellow in Europe? A possible explanation, 35 million years in the making.
  Sports
Sports Nut
Sept. 18 2014 11:42 AM Grandmaster Clash One of the most amazing feats in chess history just happened, and no one noticed.