What’s the deepest depth a submarine has gone?

Submarines are technological marvels that allow humans to explore the depths of the ocean. As submarine technology has advanced over the years, these underwater vessels have been able to reach increasingly greater depths. But what is the deepest depth that a submarine has ever traveled to? Read on to learn about the ultra-deep diving submarines that have pushed the boundaries of underwater exploration.

Key Facts About Deep Diving Submarines

Here are some quick facts to know about the deepest diving submarines:

  • In 1960, the Bathyscaphe Trieste reached the deepest known point in the ocean, the Challenger Deep in the Mariana Trench, at a depth of 10,915 meters (35,810 feet).
  • Today, the limit for deep diving military submarines is about 600 meters (2,000 feet).
  • Civilian or scientific subs can go much deeper. The current depth record for a manned civilian sub is held by the Triton 36000/2, which reached 10,000 meters (32,800 feet) in 2020.
  • Unmanned remotely operated vehicles (ROVs) and autonomous underwater vehicles (AUVs) can explore even greater depths.

Early Ultra-Deep Diving Subs

In the early days of submarine technology, depths greater than 300 meters were considered extreme. But innovations in submarine design rapidly pushed this limit deeper.

Here are some key milestones in early deep diving submarines:

  • In 1934, the Bathyscaphe, built by Auguste Piccard, reached a depth of 3,150 meters (10,330 feet).
  • In 1948, the Bathyscaphe FNRS-2, built by Piccard for the Belgian Institute for Scientific Research, reached 4,000 meters (13,100 feet).
  • In 1953, the Trieste, built by Swiss scientist Auguste Piccard, reached 3,150 meters (10,330 feet) with Trieste I and later 4,500 meters (14,760 feet) with Trieste II.

These early subs pushed the boundaries but did not yet achieve the deepest point in the ocean.

The Challenger Deep

The Challenger Deep, located in the Mariana Trench in the western Pacific Ocean, is the deepest known point in the world’s oceans. Its depth was measured at 10,925 meters (35,814 feet) below sea level by the H.M.S. Challenger expedition in 1875.

For nearly a century after that expedition, no manned vessel visited this deepest point. It was not until 1960 that humans finally traveled to the bottom of the Challenger Deep, when Swiss scientist Jacques Piccard and United States Navy Lieutenant Don Walsh descended in the Bathyscaphe Trieste.

The Bathyscaphe Trieste

The Trieste was a Swiss-designed, Italian-built benthic research submarine specifically created to withstand the enormous pressures of the deep ocean.

Key facts about the Trieste:

  • It was built in Italy in 1953 and purchased by the United States Navy in 1958.
  • It featured a large round float filled with 17,000 gallons of gasoline for buoyancy.
  • It had two small passenger compartments suspended beneath the float.
  • It was equiped with Danforth anchors to allow it to land on the seafloor.

On January 23, 1960, Jacques Piccard and Don Walsh boarded the Trieste and descended to the Challenger Deep. After a 4 hour 48 minute descent, they landed on the seafloor at a depth of 10,916 meters (35,813 feet), the deepest point ever reached by humankind.

The Trieste spent about 20 minutes on the ocean bottom before beginning its 3 hour 15 minute ascent. Its successful journey demonstrated that humans could travel to the deepest place on Earth and survive.

Later Deep Diving Submersibles

Since 1960, further technological advances have allowed submersibles to travel to even greater depths. Here are some key deep diving vessels after the Trieste:

The DSV Alvin

  • Alvin was built in 1964 and is operated by the Woods Hole Oceanographic Institution.
  • It was first certified to 6,000 meters (19,700 feet) and made over 4,600 dives.
  • In 1973, Alvin discovered hot springs and strange life forms on the seafloor, changing theories about the deep ocean.
  • After upgrades, it is now certified to 4,500 meters (14,760 feet).

The Shinkai 6500

  • The Shinkai 6500 is a Japanese manned research submersible built in 1990.
  • It was the world’s deepest diving research sub until 2020, certified to 6,500 meters (21,300 feet).
  • It features a titanium alloy hull and a variety of sampling and photographic equipment.
  • The Shinkai 6500 discovered many new deep sea creatures and is still in operation today.

The Deepsea Challenger

  • The Deepsea Challenger was engineered by filmmaker James Cameron and reached the Challenger Deep in 2012.
  • With a strong tapered body, it descended vertically and unmanned to 10,908 meters (35,787 feet).
  • Cameron then descended solo in a smaller steel sphere and filmed the Challenger Deep seabed.
  • Cameron was only the third person to reach the Challenger Deep after Piccard and Walsh.

Deepest Dives by Military Submarines

Military submarines are not designed for extreme deep diving but are built to withstand much greater pressures than civilian vessels. Here are some of the deepest dives by military subs:

  • During the Cold War, the spy sub USS Halibut reached 1,830 feet (557 m) in tests, but its typical missions were around 400 feet (122 m).
  • The Soviet Komsomolets nuclear attack sub sank in 1989 to 1,680 feet (512 m).
  • The limit for US Navy subs is publically reported as 800 feet (244 m) but unofficial speculated estimates are around 3,000 feet (915 m).
  • China’s Shang sub is estimated to dive in excess of 3,000 feet (915 m), one of the deepest military subs.

Most military subs operate at relatively shallow depths to remain stealthy. But a few can likely dive quite deep, with the deepest below 3,000 feet (915 m).

Deepest Dives by Civilian or Scientific Submersibles

While military submarines have more limited depth capabilities, civilian or scientific submersibles are engineered specifically for the deepest dives.

Here are some record-setting civilian/research subs and their deepest descents:

  • Bathyscaphe Trieste: 10,916 m (35,813 ft) to Challenger Deep in 1960.
  • DSV Alvin: 4,500 m (14,760 ft) certified depth.
  • Mir-1: 6,000 m (19,685 ft) in a series of Arctic Ocean dives in 1990.
  • Shinkai 6500: 6,500 m (21,325 ft) certified depth.
  • Triton 36000/2: 10,068 m (33,092 ft) in the Java Trench in 2020, the current overall depth record.

The Triton 36000/2’s 2020 dive broke the prior record set by the Trieste in 1960 by over 150 meters. This shows civilian deep diving technology continues advancing even after so many decades.

Unmanned Subs: ROVs and AUVs

Remotely operated underwater vehicles (ROVs) and autonomous underwater vehicles (AUVs) are unmanned, uncrewed submarines. They can explore deeper depths than manned subs for greater safety.

Here are some record-setting unmanned deep dives:

  • In 1995, the Japanese ROV Kaiko reached 10,911 m (35,798 ft), only 4 meters shallower than the Challenger Deep.
  • In 2009, the hybrid ROV Nereus dove to 10,902 m (35,768 ft) in the Challenger Deep.
  • In 2011, James Cameron’s Deepsea Challenger ROV descended to 10,908 m (35,787 ft).
  • In 2017, the Chinese Haidou-1 AUV dove to 10,708 m (35,130 ft).

With ROVs and AUVs, humans don’t face the risks of traveling to extreme depths themselves. This allows unmanned subs to keep pushing the depth limits farther.

Deepest Possible Depth for Submarines

What is the maximum depth possible for submarines with current technology? Engineers estimate about 35,000 feet (10,668 meters) is the deepest subs can practically go today.

Key limitations include:

  • Hull pressure limits based on steel yield strength.
  • Buoyancy limitations of syntactic foam.
  • Energy demands of life support systems.
  • Electronic and propulsion component pressure tolerances.

While unmanned ROVs may be engineered to slightly greater depths, 35,000 feet is approximatey the limit for manned subs. Further technological improvements will be required to make even deeper dives practical.

Challenges of Ultra-Deep Submersibles

Why have submarines not traveled deeper than about 35,000 feet so far? There are some key engineering challenges involved in designing vessels for extreme depths:

  • Pressure: The colossal pressures at ocean depths over 6,000 meters can crush most vessels. Special pressure hulls are required made of heavy exotic metals.
  • Buoyancy: floats filled with gasoline provided buoyancy for early subs, but modern syntactic foam is needed at extreme depths.
  • Propulsion: Traditional propellers cavitate at very high pressures. Some form of propellerless propulsion must be used.
  • Life Support: It consumes much more energy to provide oxygen and scrub carbon dioxide at great depths.
  • Electronics: Finding electronic components rated for both high pressures and seawater is challenging.
  • Cost: Ultra-deep subs require expensive exotic materials and are challenging to engineer and test.

These obstacles make travel past around 35,000 feet depth hugely difficult. But steady improvements in materials science, energy storage, electronics fabrication and other areas may someday allow even deeper journeys.

Future Challenges: The Hadal Zone

Traveling to the bottom of Challenger Deep and other areas from 6,000-11,000 meters deep has been called voyaging to the “hadal zone.” This zone is named after the underworld god Hades from Greek mythology.

Beyond 11,000 meters deep exists the aptly named “ultra-hadal zone” between 11,000-20,000 meters depth. This incredibly hostile environment has crushing pressures over 1,100 atmospheres and is pitch black. No manned vessel has ever reached the ultra-hadal zone yet.

Traveling to the ultra-hadal zone in a manned submarine may be the next great challenge for deep sea explorers. Engineers continue working on submersibles capable of diving deeper to discover the secrets of the deepest ocean trenches.


In summary, the absolute deepest depth reached by a submarine so far is 10,925 meters (35,813 feet), achieved by the Bathyscaphe Trieste at the bottom of the Challenger Deep in 1960.

No other manned vessel has traveled deeper since then. However, unmanned ROVs and AUVs have subsequently explored depths very close to, and in some cases marginally exceeding, Trieste’s record descent.

Modern submarines’ maximum depth limit is about 600 meters for military subs, and 10,000 meters for civilian research vessels. ROVs may be able to go somewhat deeper in the future.

Reaching the “ultra-hadal” depths of 11,000-20,000 meters remains a huge future challenge for submersible engineers. But steady improvements in technology will likely allow people to continue probing the ocean’s deepest places.

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