The Indo-Pacific region is experiencing a big change under the water. The India-China undersea rivalry is heating up as both countries race to control the deep sea. In this underwater battlefield, China has already taken a strong lead.
China’s Rapid Rise in Undersea Power Amid India-China Undersea Rivalry
According to a 2024 report by the U.S. Department of Defense (DoD), China now has the largest submarine fleet in the world by number. This growing force plays a key role in the India-China undersea rivalry, helping China expand its influence over major sea lanes—those watery highways that ships use to move goods and oil—especially in the Indian Ocean and beyond. As the India-China undersea rivalry intensifies, strategic control of these vital routes is becoming more important than ever.
China currently operates around 60 submarines, which include:
- 6 Jin-class nuclear-powered submarines that carry ballistic missiles (called SSBNs),
- 6 Shang-class nuclear-powered attack submarines (SSNs), and
- 48 diesel-electric submarines (SSKs), many using advanced technology like air-independent propulsion (AIP) to stay quiet and hidden longer underwater.
The Jin-class submarines are especially powerful. Each can carry 12 JL-2 missiles, which can hit targets far away, even in parts of the U.S., while staying safe near China’s coast. Reports say China is upgrading these subs to launch longer-range JL-3 missiles, which could travel over 10,000 kilometers—further shifting the balance in the India-China undersea rivalry.
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China is building a new type of submarine—the Type 096 SSBN—which experts expect to be even quieter and deadlier, giving China a significant advantage in the ongoing India-China undersea rivalry.
China uses Shang-class nuclear-powered submarines to attack enemy ships and land targets. The newer Shang III (Type 093B) models are guided-missile subs that may carry Land Attack Cruise Missiles (LACMs), boosting China’s offensive capabilities in the ongoing India-China undersea rivalry.
China also operates 21 Yuan-class submarines with AIP systems, expected to grow to 25 by 2025. Alongside 10 Russian Kilo-class and 13 older Song-class subs, this gives China a large and varied fleet. A new AI-driven torpedo system now helps Chinese subs better identify real threats, strengthening their edge in the India-China undersea rivalry.
To further dominate the deep sea, China is upgrading its nuclear submarines with pump-jet propulsion and noise-reduction tech. These improvements support China’s goal of power projection and sea control in the Indian Ocean Region (IOR)—a vital area for global trade and energy routes.
India’s Modernization and Strategic Push in the India-China Undersea Rivalry
India is also boosting its submarine strength, but it still has a smaller and less advanced fleet compared to China. According to the World Directory of Modern Military Warships (WDMMW) 2025, India currently has 19 active submarines, including:
- 3 nuclear-powered SSBNs
- 16 diesel-electric conventional submarines
India’s nuclear submarines are known as Arihant-class. These form a key part of the country’s sea-based nuclear shield, playing a critical role in the India-China undersea rivalry. The first, INS Arihant, entered service in 2016. India equipped it with K-15 missiles that can travel 750 km and is now upgrading it to carry K-4 missiles with a range of 3,500 km—an important move as the India-China undersea rivalry intensifies.
The second nuclear submarine, INS Arighat, was added in August 2024. It features upgraded systems and more missile space, giving India greater flexibility underwater. A third, INS Aridhaman, launched in 2021, is expected to join the fleet by the end of 2025, further boosting India’s position in the India-China undersea rivalry.
On the conventional side, India has built six Kalvari-class submarines under Project 75, using French technology. These silent submarines carry torpedoes and Exocet missiles. The newest addition, INS Vagsheer, was commissioned in January 2025.
India also operates:
- Seven Russian-built Kilo-class submarines, now getting upgrades
- Four German Shishumar-class submarines, some of which are used for training. These are expected to retire after 2035
But there are issues too. Many Indian submarines are old, and building new ones has been delayed. Reports from India Today and The Hindu highlight the slow pace of submarine construction.
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To fix this, India is working on a new version of its Air-Independent Propulsion (AIP) system, which will be added to the Kalvari-class subs starting with INS Kalvari between 2025 and 2026, as reported by Naval News.
Another project, called Project 75(I), aims to build six next-generation AIP-equipped submarines with help from Germany’s ThyssenKrupp and Indian companies. This is part of India’s larger “Make in India” plan, focusing on local defense production, according to Defense.info and India Today.
India is also watching China’s moves carefully. Chinese port projects in Pakistan, Sri Lanka, Myanmar, and Africa have raised alarms in New Delhi. These are part of China’s “String of Pearls” strategy, which includes:
- Gwadar Port in Pakistan
- Hambantota Port in Sri Lanka
- Kyaukpyu Port in Myanmar
- Chittagong in Bangladesh
- Port Sudan and Djibouti, where China has a military base since 2017
While China says these are for trade, Indian defense experts worry they could be used by the People’s Liberation Army Navy (PLAN) for military purposes. These ports could help China refuel, resupply, and spy on Indian naval movements in the IOR.
To respond, India has launched a “Necklace of Diamonds” strategy. This involves working closely with nearby coastal nations and Quad allies like Australia, Japan, and the United States, according to The Times of India.
India-Australia Undersea Surveillance Pact Takes Shape
A major new step in India’s undersea strategy is its surveillance agreement with Australia. This is the first science and technology deal between the two countries focused only on underwater defense.
Announced by the Australian Department of Defense, this pact will improve both nations’ abilities to detect submarines and unmanned underwater vehicles early, which is important for preventing surprise attacks.
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This is a three-year project, bringing together:
- Australia’s Defense Science and Technology Group (DSTG)
- India’s Defense Research and Development Organization (DRDO)
The two sides will share data, build joint algorithms, and conduct tests to improve underwater tracking systems. Dr Arulampalam from DSTG said the project will focus on acoustic sensing and signal processing, which are vital for spotting stealth submarines.
This agreement comes at a time when undersea competition is intense, especially with China’s strong submarine fleet and new AI technologies. For both India and Australia, this pact is a sign of their growing defense ties and shared goal of keeping the Indo-Pacific region safe and stable.
