India’s deep-sea adventure: Samudrayaan’s Matsya ready for 6,000-metre dive in push to join elite club

India is preparing to embark on a deep-sea mission of unprecedented scale — one that will send its scientists 6,000 metres beneath the ocean’s surface, a feat accomplished by only a handful of countries. Titled Samudrayaan, the expedition marks India’s first manned dive to such depths, placing it among an elite global cohort and extending its exploratory reach from the skies to the seafloor.

At the heart of the mission is Matsya, a 25-tonne submersible with a titanium hull, built to brave the crushing pressure and icy dark of the deep ocean. Designed to carry three crew members, Matsya will facilitate biological sampling, mineral exploration, and environmental monitoring in one of Earth’s most extreme environments.

The mission is currently in its preparatory phase, with a 500-metre test dive slated for the end of this year. The full 6,000-metre descent will follow in stages. Each dive is expected to last about eight hours — four for the descent and four for the return journey.

Key facts about Matsya

Matsya is entirely indigenous, developed using Indian technology and expertise. Its 2.1-meter-diameter crew sphere, made of a titanium alloy, is engineered to maintain an internal pressure of 1 atmosphere despite facing more than 600 times the surface pressure at full depth. The spherical hull has been tested to withstand 720 bars — 20% more than the anticipated pressure at 6,000 metres.

Human safety remains paramount. A Det Norske Veritas (DNV)-certified Human Support and Safety System (HSSS) maintains oxygen at 20%, carbon dioxide below 1000 ppmv, and monitors humidity through sensors. The sub is designed for 12-hour operations with an emergency endurance of up to 96 hours.

Communication is maintained through an Underwater Acoustic Telephone, tested to 10,000 metres. The pilot checks in every 30 minutes with the ship-based Mission Control Centre. A sub-phone rated for shallower operations provides redundancy.

Matsya is also designed to naturally float unless made to dive by flooding its ballast tanks. For resurfacing, it employs three weight-drop mechanisms and carries additional emergency power, control, and communication systems.

The mission aims to retrieve data and samples that could advance marine science, pharmaceutical research, and climate modeling — potentially redefining India's scientific frontier beneath the sea.