What Is a Submarine? Underwater Warship Explained

# What Is a Submarine? Underwater Warship Explained

Quick answer: A submarine is a warship that can dive below the surface and operate underwater for days, weeks, or even months. Submarines hunt enemy ships, fire missiles, gather intelligence, and carry the world’s most destructive weapons — sea-launched nuclear missiles.

A submarine is essentially a steel tube full of crew and weapons that can adjust how much water vs air is inside it to sink or rise.

How a Submarine Dives

A submarine has ballast tanks along its sides:

Surface mode: tanks full of air → boat floats
Dive: open vents, water rushes in, tanks fill with water → boat sinks
Surface again: compressed air pushes water out → boat rises

Once submerged, the sub controls depth with diving planes (small wings) and ballast water adjustments.

The Three Main Types

Type	Power	Endurance	Use
Diesel-Electric (SSK)	Diesel + battery	Days underwater	Coastal defense, hunting
AIP (Air-Independent Propulsion)	Diesel + AIP + battery	2–3 weeks underwater	Modern stealth subs
Nuclear (SSN/SSBN)	Nuclear reactor	Months underwater (food/water limits, not power)	Blue-water navies

Diesel-Electric Submarines

Run diesel engines on the surface or with snorkel
Charge batteries during diesel operation
Run silent on batteries when submerged
Must surface every few days to recharge
Cheap, simple, very common worldwide

Examples: Type 209 (German export, used by Türkiye Atılay-class), Kilo (Russia), Songwon (NK)

AIP Submarines — The Modern Standard

AIP = Air-Independent Propulsion. Adds a system that produces power without surface air, letting subs stay submerged 2–3 weeks. Methods:

Stirling engine (Sweden, Japan, China)
Fuel cells (Germany Type 212/214)
MESMA (closed-cycle steam, France)

AIP subs are very quiet — often quieter than nuclear subs.

Famous AIP subs:

Type 214 (Germany) — used by Türkiye Reis-class, S. Korea, Portugal, Greece
Soryu-class (Japan)
Scorpène-class (France)
A26 Blekinge (Sweden)

Nuclear Submarines

A nuclear reactor produces unlimited heat/electricity. Only food, water, and crew mental health limit how long they can stay submerged. Some have stayed under for 6+ months.

Two types:

SSN (Submarine, Nuclear, attack) — hunts ships and other subs
SSBN (Submarine Ballistic Nuclear) — carries nuclear missiles

Famous nuclear subs:

Virginia-class SSN (USA)
Seawolf-class SSN (USA, only 3 built — most expensive ever)
Astute-class SSN (UK)
Yasen-class SSN (Russia)
Akula-class SSN (Russia)
Ohio-class SSBN (USA, 14 boats, each carries 20 Trident missiles)
Borei-class SSBN (Russia)
Type 094 / 096 SSBN (China)

Famous Submarine Weapons

Heavyweight torpedoes (Mk 48, UGST, Akya) — sink ships and other subs
Anti-ship missiles — Tomahawk (USA), 3M-54 Kalibr (Russia), Atmaca (Türkiye)
Land-attack cruise missiles — Tomahawk, Kalibr, Storm Shadow
Sub-launched ballistic missiles (SLBMs) — Trident II, R-30 Bulava, JL-3
Mines

Why Submarines Are So Powerful

1. Stealth — water absorbs radar, sound is hard to track
2. Surprise — can attack anywhere along a coast
3. Survivability — hard to find means hard to destroy
4. Strategic reach — SSBNs guarantee second-strike capability
5. Cost-effective — one nuclear sub can deter entire navies

This is why every major navy operates submarines — and many minor navies too.

How Submarines Are Detected

Detection is hard but possible:

Active sonar — sends pings, listens for echoes (loud, gives away searcher)
Passive sonar — listens silently for sub’s engine noise
MAD (Magnetic Anomaly Detection) — large metal object disturbs Earth’s field
Wake detection — by satellite or radar
Periscope detection — when sub goes shallow
SOSUS — undersea hydrophone arrays

Modern AIP and nuclear subs are extremely quiet. Hunting one can take days or weeks.

ASW — Anti-Submarine Warfare

Forces designed to hunt subs:

Maritime patrol aircraft (P-8, P-1, ATR-72 MPA)
ASW helicopters (MH-60R Romeo, NH-90 NFH)
Frigates with sonar and helicopters
Other submarines (cat-and-mouse)
Mines

The 1982 Falklands War, 1971 India-Pakistan War, and Cold War sub-vs-sub games all featured intense ASW.

Türkiye’s Reis-Class — Quick Spotlight

Türkiye is building 6 Type 214TN AIP submarines:

Piri Reis (2024 commissioning)
Hızır Reis
Murat Reis
Aydın Reis
Seydi Ali Reis
Selman Reis

Specs:

1,800+ tons submerged
8 torpedo tubes (533 mm)
Hydrogen fuel cell AIP
21 days underwater endurance
Akya heavyweight torpedo (domestic, Roketsan)
Atmaca submarine-launched variant planned

Built at Gölcük Naval Shipyard with German TKMS technology transfer.

Recent Submarine Wars

WWII — German U-boats nearly starved Britain; Allied ASW victory turned the tide
Cold War — US/Soviet sub cat-and-mouse, often dangerous near-misses
1982 Falklands — HMS Conqueror (SSN) sank ARA General Belgrano with torpedoes
2010 — North Korean sub torpedoed South Korean corvette ROKS Cheonan (46 sailors killed)
2022+ Ukraine — Russian Kilo subs fired Kalibr missiles at Ukrainian cities

A Kid-Friendly Analogy

Imagine a sealed steel football that can:

Take in air or water to sink or float
Move using a hidden propeller
Listen to everything around it with super-ears (sonar)
Shoot bombs from inside
Stay hidden for weeks

That’s a submarine — except football-sized would only hold one mouse; real ones are the size of a small skyscraper.

How Big Are Submarines?

Class	Length	Crew
Reis-class (Türkiye)	68 m	27
Virginia-class (USA)	115 m	132
Ohio-class SSBN (USA)	170 m	155
Borei-class (Russia)	170 m	107
Typhoon-class (Russia, retired)	175 m, 48,000 tons	160 — largest ever built