The Deepest-Diving Submarines of 2026, Ranked
South Korea's Chang Bogo-class submarine has the deepest publicly disclosed test depth in our database at 500 meters, ahead of Russia's Akula and Borei classes.
Via Wikipedia, Jang Bogo-class submarine (shown for identification)
South Korea’s Chang Bogo-class has the deepest publicly disclosed test depth of any submarine in the WeaponSpecs database: 500 meters. Russia’s Akula-class and Borei-class follow at 480 meters, Turkey’s Reis-class at 400 meters, and Russia’s Kilo-class and France’s Scorpene-class tie at 300 meters. That’s the full ranking, and it comes with an important caveat up front.
Of the roughly 32 submarine classes tracked in the WeaponSpecs database, only these six publish a test depth figure at all. Test depth is one of the most sensitive numbers in undersea warfare, it tells an adversary how deep a boat can go to break contact or dodge a torpedo, so most navies and manufacturers simply don’t release it. This ranking is therefore a partial, self-selecting list: it ranks the submarines willing to disclose the number, not the deepest-diving submarines in the world. Boats with no public figure could easily dive deeper than everything below. Read the ranking as “deepest among those who talk,” not “deepest, full stop.”
Why do so few submarines publish a test depth?
Test depth is the maximum depth a submarine is certified to operate at repeatedly under normal conditions, distinct from crush depth, which is the point of structural failure. Both numbers describe how a hull performs under exactly the kind of pressure an adversary would want to know about before a fight. A navy that reveals its boats can dive to 500 meters has told every rival sonar operator and torpedo designer something concrete about where that boat can and cannot hide. That’s a rare trade in military disclosure, most navies would rather let the number stay classified than hand over a data point that shapes how someone else hunts them.
The six classes in this ranking are the exception, not the rule, and the reasons they’ve gone public vary. Export-oriented programs like South Korea’s Chang Bogo-class and France’s Scorpene-class have some incentive to publish performance figures for potential buyers. State-run defense messaging, which is the more likely explanation for the Russian figures here, serves a different purpose: signaling capability to rivals and domestic audiences alike. Either way, a published number is a choice, not just an inevitability of engineering documentation, and that choice should shape how much weight you put on the figure.
How do the six ranked submarines compare?
| Rank | Submarine class | Country | Test depth | Submerged speed |
|---|---|---|---|---|
| 1 | Chang Bogo-class | South Korea | 500 m | 21.5 kn |
| 2 | Akula-class (Project 971) | Russia | 480 m | 33 kn |
| 3 | Borei-class | Russia | 480 m | 29 kn |
| 4 | Reis-class | Turkey | 400 m | 20 kn |
| 5 | Kilo-class (Project 636.3) | Russia | 300 m | 20 kn |
| 6 | Scorpene-class | France | 300 m | 20 kn |
Three of the six figures, Akula, Borei, and Kilo, are Russian state or manufacturer disclosures. None of them have been independently verified by Western naval intelligence agencies in open-source reporting, and readers should treat them the way we treat every state-sourced spec on this site: as a claim with a plausible engineering basis, not as a confirmed fact. That doesn’t mean they’re inflated, Soviet and Russian submarine design has a long, credible pressure-hull tradition, but the distinction between “disclosed” and “verified” matters, especially for a figure this sensitive.
Why does Chang Bogo lead a field of larger, more famous submarines?
The Chang Bogo-class isn’t the biggest or best-known name in this group, but it tops the list on the one number this ranking actually measures. South Korea’s submarine program has developed rapidly over the past two decades, largely through licensed and indigenized diesel-electric designs, and its export ambitions plausibly explain why a test depth figure exists in public documentation at all. Whether 500 meters reflects a genuinely more capable hull, a more conservative certification margin, or simply a different disclosure policy than Russia’s is impossible to say from a spec sheet alone. The number is real in the sense that it’s what’s published, not necessarily in the sense that it’s been checked by anyone outside the manufacturer.
What explains Akula’s speed advantage over Borei at a similar depth?
The most interesting contrast in this table isn’t depth, it’s speed. Akula-class and Borei-class share the same disclosed 480-meter test depth, but Akula’s submerged speed of 33 knots dwarfs Borei’s 29 knots, and both dwarf every conventionally powered boat on this list. That gap tracks mission, not raw engineering ambition. The Akula is a nuclear-powered attack submarine (SSN), built to hunt other submarines and surface ships, a role that rewards speed for closing on a target or breaking away from one under pursuit. The Borei is a nuclear-powered ballistic-missile submarine (SSBN), a strategic deterrence boat built to disappear on a patrol lasting months, where staying quiet and undetected matters more than outrunning anything. Two Russian nuclear boats, similar depth rating, very different speed profiles, because they’re built to win different fights.
Does a deeper test depth actually mean a better submarine?
No, and this ranking shouldn’t be read that way. Test depth is a single structural and evasion variable in a system where acoustic signature, sonar suite, weapons load, crew proficiency, and mission profile all matter as much or more. A submarine that can dive to 500 meters but runs loud getting there may be easier to detect and track than a 300-meter boat with a quieter hull and better-isolated machinery. Depth extends the space a boat has to maneuver, break a torpedo’s terminal seeker lock, or use the thermal layers and pressure gradients of deep water to mask its position, but it’s a tool within a broader capability picture, not a standalone verdict on which submarine wins.
It’s also worth restating the limitation this entire piece rests on: this is a ranking of six submarines out of roughly 32 in the WeaponSpecs database, built entirely from the subset willing to publish the number. Most classified navies, and likely some of the most capable submarines in service today, simply don’t appear here because the figure never made it into open literature. Read this table as a snapshot of disclosure, not a definitive depth-rating of the world’s submarine fleets.
Where to go from here
If you’re evaluating a submarine procurement or just want the full underlying data, WeaponSpecs’ compare tool lets you set any two boats side by side on depth, speed, and everything else in the database, the submarine type page rounds up every class we track including the ones without a public depth figure, the advisor can walk through a mission-specific recommendation instead of a generic ranking, and the articles page has more of these data-first breakdowns across other weapon classes.
Systems in this comparison
Every system covered above, with its photo and, where available, a video. Tap a card to open the full spec sheet.
Compare these side by side →
Submarine
Chang Bogo-class submarine
Submarine
Akula-class (Project 971)
Submarine
Borei-class
Submarine
Reis-class
Submarine
Kilo-class (Project 636.3)
Submarine
Scorpene classFrequently asked questions
What is the deepest-diving submarine in the WeaponSpecs database? +
South Korea's Chang Bogo-class has the deepest publicly disclosed test depth on record at 500 meters. It is followed closely by Russia's Akula-class and Borei-class, both listed at 480 meters, though those are state-disclosed figures rather than independently verified ones.
Why don't most submarines have a public test depth figure? +
Test depth (and the related crush depth) is one of the most closely guarded numbers in naval engineering, because it tells an adversary exactly how deep a boat can dive to evade sonar and torpedoes. Of the roughly 32 submarine classes in the WeaponSpecs database, only six publish a test depth at all. The rest either classify it outright or simply don't disclose it in open literature.
Are Russian-disclosed submarine figures reliable? +
Treat them as claims, not confirmed facts. The Akula, Borei, and Kilo figures in this ranking all originate from Russian state or manufacturer disclosures and have not been independently verified by Western naval intelligence agencies in open-source reporting. That doesn't make them wrong, but it does mean they carry a different evidentiary weight than a figure confirmed by a third party.
What's the difference between a nuclear attack submarine and a nuclear ballistic-missile submarine (boomer)? +
Both can be nuclear-powered, but they're built for different jobs. Attack submarines like the Akula-class are designed to hunt other submarines and surface ships, which rewards speed for pursuit and evasion. Ballistic-missile submarines like the Borei-class are built around deterrence patrols, staying hidden for months at a time, which rewards quiet endurance over top speed.
Does a deeper test depth make a submarine better? +
Not by itself. Test depth is one variable among many, alongside acoustic signature, sensor suite, weapons load, and crew training, that determine how effective a submarine actually is. A boat that dives deeper but runs louder doing it may be easier to find than a shallower, quieter one. Depth matters most as an evasion and structural-margin figure, not a standalone measure of capability.
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