Deepest-ever Indian dive: Two aquanauts reach record depths in Atlantic, prep for Samudrayaan Mission

The Matsya6000 vessel that will carry the aquanauts 6000 metres under the sea. (Express Photo)

The training dives also underline a rare collaboration. France opened access to one of the world’s few submersibles capable of such depths after months of back-and-forth, at a time when most nations guard deep-sea technology closely. The Nautile gave the Indian team more than a seat — it gave them first-hand exposure to mission protocols, vessel handling, and recovery operations.

Like the Axiom-4 mission’s role in preparing astronaut Shubhanshu Shukla for Gaganyaan, the Nautile dives gave India’s deep-sea crew end-to-end operational training crucial for Samudrayaan — from pre-dive preparations and vessel piloting to manipulator arm operations, tracking, and retrieval.

“We will have an Indian going to space and another diving 6,000 metres under the sea in our own mission by 2027. Our deep sea mission is coinciding with the mission to space — even these dives and Shubhanshu Shukla’s travel to the International Space Station have coincided. Both these sectors, which have remained underexplored, will play a significant role in *Viksit Bharat*,” Union Science Minister Dr Jitendra Singh said.

From deployment to retrieval, the 5,000-metre dive lasted about 9.5 hours. “It took around 2.5 hours to reach the depth. I spent four hours there, working with the robotic arm, practising operations with and without light in a place with no sunlight, checking life support systems if CO₂ scrubbers are shut off, and running drills for power failure or emergency ascent,” said Singh, a former Naval submarine pilot.

One key learning was in communication. “Thousands of metres underwater, normal radio-based communication does not work as radio waves cannot penetrate water. We use acoustic telephones that transmit sound waves — but with a delay of a few seconds,” said Dr M Ravichandran, Secretary, Ministry of Earth Sciences.

India has already developed its own acoustic phones and the titanium sphere for Samudrayaan, with the latter being manufactured by ISRO to exacting specifications — 80 mm thick with no more than a 0.2 mm deviation, as even a slight flaw could cause collapse under extreme pressure.

Samudrayaan is part of the country’s Deep Ocean Mission, which will, for the first time, take a three-member crew 6,000 metres below the surface in the indigenously developed Matsya6000 submersible. The mission aims to develop technologies to access and transport tonnes of valuable minerals from the ocean-bed in an environmentally safe manner. Equipped with scientific sensors and tools, Matsya6000 can operate for 12 hours, extendable to 96 in emergencies. Only five countries — the USA, Russia, China, France, and Japan — have so far carried out successful crewed deep-ocean missions; India is set to join this exclusive club.

Under the current mission plan, a shallow-water dive to 500 metres using a simpler steel sphere is scheduled for mid-2026, followed by integration of the titanium sphere and deep-water trials in mid-2027. The final 6,000-metre mission is slated for 2027-28.