An official website of the United States Government 
Here's how you know

Official websites use .gov

.gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS

A lock ( lock ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Hitting Bottom: Submariner Explored Deepest Part of Ocean

You have accessed part of a historical collection on Some of the information contained within may be outdated and links may not function. Please contact the DOD Webmaster with any questions.

Thousands have climbed Mount Everest, and a handful of people have walked on the moon. But reaching the lowest part of the ocean? Only three people have ever done that, and one was a U.S. Navy submariner.

In the Pacific Ocean, somewhere between Guam and the Philippines, lies the Marianas Trench, also known as the Mariana Trench. At 35,814 feet below sea level, its bottom is called the Challenger Deep — the deepest point known on Earth. In fact, to put it into perspective, think about the Titanic, which was found 12,600 feet below the surface of the Atlantic Ocean — nearly 2.4 miles down.

The Challenger Deep is nearly three times deeper than that.

A map of the Western Pacific Ocean.
Western Pacific Ocean
A map of the Western Pacific Ocean showing the location of Marianas Trench and Kermadec Trench. Challenger Deep is the deepest point of the Marianas Trench. The Sirena Deep is the second-deepest part.
Photo By: U.S. Geological Survey
VIRIN: 150607-O-ZZ999-772C

Testing Pressure

Only three people have ever made it to the Challenger Deep. The first two did it 59 years ago this week: Navy Lt. Don Walsh, a submariner, and explorer Jacques Piccard.

Walsh’s engineering background allowed him to be a test pilot for the Trieste, a deep-diving research submersible purchased on behalf of the Navy. The rig was specially equipped with 5-inch-thick steel walls to withstand immense pressures — eight tons of pressure per square inch, to be specific, which is like 2,365 pounds sitting on a person’s fingernail.

Two men load iron shot ballast into a submersible.
Trieste Test
Jacques Piccard, right, co-designer of the Trieste, and Ernest Virgil load iron shot ballast into the sub prior to a test descent into the Marianas Trench, Nov. 15, 1959.
Photo By: Navy Photo
VIRIN: 591115-N-ZZ999-772C

On Jan. 23, 1960, Walsh and Piccard made history when they made the five-hour, 6.78-mile odyssey to the world’s deepest-known point.

A Different World

What did they find there? Walsh talked about his experience in an interview with the Office of Naval Research, so we’ll let him explain:

“As we approached the seafloor, we could see it coming up, and we did see about a foot-long flatfish, like a halibut or sole — small. But that told us quite a bit, just that one glimpse, because that’s a bottom-dwelling form — two eyes on one side — and if there’s one, there’s more. That tells you there’s also sufficient oxygen and food at that depth because they’re bottom dwelling,” Walsh said.

A black-and-white photo of two men in a submersible.
Tight Quarters
Navy Lt. Don Walsh and explorer Jacques Piccard sit inside the Trieste, the submersible they used to descend to the Challenger Deep — the deepest spot in the world’s oceans — in 1960. The feat was not repeated again until 2012, when movie director James Cameron returned to the same spot in a small submarine.
Photo By: Navy Photo
VIRIN: 600110-N-ZZ999-924

“We did not see anything at the bottom once we landed because the bottom sediment stirred up, and it was like somebody painted our viewport white,” he continued. “We spent a half-hour on the bottom, and the rest of the time coming up. And that was it.”

That might not seem like much to some, but it opened up a whole new world for explorers.

Undersea Exploration & the Navy

The Navy has always been interested in undersea exploration for navigation, scientific research, education and strategic purposes. In fact, by 1958, it funded nearly 90 percent of all U.S. oceanographic ventures.

Three men on the back of a boat lower an autonomous underwater vehicle into water.
Naval Academy Midshipman 1st Class Nolan Brandon, left, Ken Haulsee, center, a graduate student at the University of Delaware, and Peter Barron, a laboratory technician at the University of Delaware, lower an autonomous underwater vehicle into the water off the coast of Long Island, N.Y., to take sonar data on the wreck of the World War I-era armored cruiser USS San Diego, Sept. 11, 2017.
Photo By: Navy Petty Officer 1st Class Eric Lockwood
VIRIN: 170911-N-TH437-099C

The Trieste trip was the culmination of Project Nekton, a series of dives meant to test the viability of using manned craft at extreme depths to study marine life and how temperature, pressure and sound interact at great depths, among other scientific questions.

Whether the Navy is diving, collecting scientific data, investigating shipwrecks or testing autonomous underwater vehicles, this mission continues to evolve and has led to collaborations with many in the civilian scientific community.

Fun Facts

  • In case you were curious, the Trieste is now part of the undersea exploration exhibit at the National Museum of the U.S. Navy in Washington.
  • Since its bowels-of-the-earth voyage, only one person has returned to the Challenger Deep: explorer and filmmaker James Cameron in 2012.

Two men stand near a submersible on display.
Dive Mates
Filmmaker James Cameron, left, and Don Walsh meet by the Trieste at the National Museum of the U.S. Navy in Washington, June 10, 2013. Walsh piloted the Trieste, a deep-diving research vessel, to the deepest-known part of the earth's oceans, the Challenger Deep in the Marianas Trench near Guam on Jan. 23, 1960. Cameron was the third person to reach the Challenger Deep, on March 26, 2012, when he piloted the Deepsea Challenger.
Photo By: Navy Petty Officer 1st Class Gina K Morrissette
VIRIN: 130610-N-WE887-004C

Related Stories