India's Deep-Sea Robots Have Worked at 5,289 Metres, but the Crewed Matsya 6000 Has Only Been Tested in a Harbour

India’s Deep Ocean Mission has produced two uncrewed vehicles that have worked more than 5,000 metres below the surface and one crewed submersible that, on the public record, has been tested only in a harbour near Chennai. The uncrewed pair are ROSUB 6000, a tethered robot tested to 5,289 metres, and the Ocean Mineral Explorer (OMe 6000), an autonomous survey vehicle that worked at 5,271 metres in December 2022. The crewed vehicle is Matsya 6000, and the most recent schedule from its builders, given on 5 June 2026, puts its first 500-metre dive between October and December 2026.

What the Cabinet approved on 16 June 2021

The Cabinet Committee on Economic Affairs, chaired by Prime Minister Narendra Modi, approved the Ministry of Earth Sciences’ Deep Ocean Mission on 16 June 2021. The Press Information Bureau (PIB) release put the cost at Rs 4,077 crore over five years, spent in phases, with Rs 2,823.4 crore for the first three years, 2021 to 2024. The mission has six components. The first covers deep-sea mining technology and a crewed submersible for three people and 6,000 metres, a capability the release said only a very few countries have.

The mission began on 7 September 2021. Samudrayaan is the submersible project inside it, and Matsya 6000 is the vehicle that project is building. On 26 July 2023 Earth Sciences minister Kiren Rijiju told the Lok Sabha that Rs 1,400 crore had been allocated so far, Rs 405.92 crore disbursed and Rs 225.35 crore spent, and that the mission period was 2021 to 2026. The ministry’s Notes on Demands for Grants for 2026-27 show the mission at Rs 589.96 crore of actual spending in 2024-25, Rs 600 crore budgeted and Rs 660 crore revised for 2025-26, and Rs 625 crore budgeted for 2026-27.

The uncrewed machines that have already worked

ROSUB 6000 is a work-class remotely operated vehicle (ROV), a robot that a pilot on a ship drives through a cable. Like the inspection robots tuput has covered in radioactive rooms and mines, it works where a person cannot. The ministry’s Polymetallic Nodule Management Board started the project, and the National Institute of Ocean Technology (NIOT) in Chennai built it. A five-function grabber arm holds the vehicle steady while a seven-function manipulator does the work. NIOT says it was tested to 5,289 metres at a nodule site in the Central Indian Ocean Basin, and lists its exploration work at a gas hydrate site in the Krishna-Godavari basin and at the SONNE hydrothermal field on the South Central Indian Ridge. In September 2016 it was put down to 3,400 metres with sonar and cameras to check a target in the search for a missing Indian Air Force An-32.

OMe 6000 is an autonomous underwater vehicle (AUV), which swims a programmed route with no cable. The ministry told the Lok Sabha in 2023 that in December 2022 it was launched from the research ship Sagar Nidhi at a nodule site 5,271 metres down, inside the area India holds under contract with the International Seabed Authority. It mapped the seabed for more than 26 hours from 30 metres above it on 15 and 16 December, then photographed a strip 1 kilometre by 0.5 kilometre in 130 lines from 5 metres up on 17 and 18 December. The ministry said the images help estimate how many nodules lie on the floor and what lives among them.

A NIOT AUV also appears in a defence ministry release of 12 January 2024. Searching at 3,400 metres around the last known position of the An-32 that vanished on 22 July 2016 with 29 people aboard, it imaged debris about 140 nautical miles (310 kilometres) from the Chennai coast. The release worded the identification as possible, because no other aircraft had been reported missing in that area.

Varaha-1 is NIOT’s seabed mining machine. Mongabay India reported on 26 October 2022 that a NIOT team lowered the 9.5-tonne machine to 5,270 metres in the Central Indian Ocean in April 2021 and that the test objective was met.

Matsya 6000 and its titanium sphere

Matsya 6000 carries its three crew in a titanium sphere, and the sphere is the part that came from ISRO. The Vikram Sarabhai Space Centre designed it and developed the metal, ISRO said on 23 July 2025. The sphere is 2,260 millimetres across with an 80-millimetre wall, made of Ti6Al4V ELI alloy, and is expected to withstand an external pressure of 600 bar at minus 3 degrees Celsius, roughly 600 times the air pressure at the surface. PIB gives the inside diameter as 2.1 metres.

Joining 80 to 102 millimetres of titanium meant developing a new process. ISRO’s Liquid Propulsion Systems Centre could weld up to 20 millimetres, so it raised its electron beam welder from 15 to 40 kilowatts, upgraded an X-ray inspection facility to 7.5 million electron volts and ran nearly 700 weld trials. The first weld on actual hardware, 80 millimetres thick and 7,100 millimetres long, took 32 minutes, which ISRO says had not been done in India before. It said certification of the facilities, the process and the product by a third party was still planned.

The design target is 12 hours at 6,000 metres, with emergency endurance of up to 96 hours. Nothing tuput found in an official release says a certified 6,000-metre sphere has been delivered, or that any Matsya sphere has been pressure-tested at depth.

Every date the crewed submersible has been tested or promised

• 27 January to 12 February 2025: wet tests at the L&T shipbuilding facility at Kattupalli Port near Chennai, reported by PIB on 17 February. The release counts five unmanned and five manned dives but also calls them eight dives in total, so its own numbers do not agree. It said underwater voice communication was less effective because the harbour was shallow, that in some areas “additional efforts are needed”, and that shallow-water demonstrations to 500 metres were planned “by the end of 2025”.
• 13 February 2025: the Rajya Sabha was told Matsya 6000 was likely to be realised by 2026.
• 5 and 6 August 2025: not a Matsya dive. NIOT scientist Raju Ramesh and retired Commander Jatinder Pal Singh descended to 4,025 and 5,002 metres in the Atlantic in the French submersible Nautile, operated by the research institute IFREMER, for about seven hours in total, PIB reported on 14 August. Minister Jitendra Singh set the achievement beside Shubhanshu Shukla’s space station flight four weeks earlier, a flight covered in tuput’s Gaganyaan article.
• 14 August 2025: the Earth Sciences secretary, M. Ravichandran, told Deccan Herald that the first 500-metre dive was delayed by about six months because the floating foam for the crew capsule was due from France by November, and that the 6-kilometre dive was scheduled for December 2027.
• 5 June 2026: NIOT director Balaji told ETV Bharat that three scientists would make a test dive to about 50 metres in July, that the February 2025 trial had reached 20 metres, and that a crewed 500-metre mission was planned for October to December 2026.

So the 500-metre date has moved from the end of 2025 to the last quarter of 2026. The 6,000-metre dive is now scheduled for December 2027, a year after the 2026 target the Rajya Sabha was given in February 2025. Tuput found no official release dated after 5 June 2026 that confirms the 50-metre dive, the foam delivery or a 500-metre dive.

The seabed the vehicles are meant to reach

India holds contracts with the International Seabed Authority (ISA), the UN body that regulates mineral activity on the seabed in international waters. The ISA register lists India’s nodule contract as signed on 25 March 2002 and running to 24 March 2027 after two extensions. The ministry gives the area as 75,000 square kilometres in the Central Indian Ocean Basin. Nodules are lumps of metal-rich rock on the sea floor, most of them two to eight centimetres across, the ISA says.

For polymetallic sulphides, the metal deposits that form around hot vents, the register lists two Indian contracts. One runs from 26 September 2016 to 25 September 2031. The other runs from 15 September 2025 to 14 September 2040 and covers 10,000 square kilometres of the Carlsberg Ridge; the ministry announced it on 20 September 2025 and said India is the first ISA member state to hold two such contracts.

The size of the nodule resource is stated two ways. A PIB release of 21 August 2017 gave 380 million tonnes, with 4.7 million tonnes of nickel, 4.29 million of copper and 0.55 million of cobalt. In a Rajya Sabha reply of 21 August 2025, Jitendra Singh gave 366 million metric tonnes with grades of 1.09 per cent copper, 1.14 per cent nickel and 0.14 per cent cobalt. Neither is a mined quantity. The 2017 release said extraction was not yet found economically viable, and the 2025 reply said the ministry had only surveyed the area.

Mining rules that do not exist yet

The 2025 reply also said deep-sea mining is not permitted at present, because the ISA has not finalised its exploitation regulations. Those rules are still open. The ISA Council met from 13 to 24 July 2026 and, Mongabay reported on 29 July, again failed to finish them. Pradeep Singh of the Oceano Azul Foundation, a marine conservation group in Lisbon, told Mongabay that “there’s not going to be any adoption this year”. Mongabay also reported that 45 countries have called for a moratorium or precautionary pause on deep-sea mining.

Indian scientists disagree about the risks. Nagender Nath, a former chief scientist at the National Institute of Oceanography, told Mongabay India that sediment plumes released at mid-depth could harm plankton and midwater animals. Rahul Sharma, also a former chief scientist there, said mining could kill organisms along the collector track, and pointed to his study in which monitoring over eight years showed recolonisation had begun after an experimental disturbance. Emma Wilson of the Deep Sea Conservation Coalition, an alliance of conservation groups with observer status at the ISA, called for a moratorium until more is known.

The ISA Council’s next scheduled session is in March 2027, Mongabay reported, and the register lists India’s nodule contract as running to 24 March 2027.