British involvement in the successful search for a missing Argentine submarine has been described as "invaluable", Sky News can reveal.

Forty-four sailors were in the ARA San Juan when it disappeared in the South Atlantic on 15 November 2017, prompting an international search.

Several nations, including the UK, spent two months helping Argentina look for the vessel before the search was called off.

Image: The ARA San Juan had disappeared in the South Atlantic on 15 November 2017

But now it has emerged that the Royal Navy provided data and analysis that allowed the marine survey firm Ocean Infinity to pinpoint the area where the submarine would be.

It was found last Friday, 800 metres down, several hundred miles from its last reported position.


The British co-operation to find an Argentinian navy ship comes after years of frosty relations following the 1982 war between the two countries over the Falkland Islands.

Ocean Infinity chief executive Oliver Plunkett told Sky News how difficult it was to find the sub, even with the help from the UK military.

Image: Oliver Plunkett, CEO of Ocean Infinity

He said: "When we start... we have to understand where is the right place to look.

"The Royal Navy, through the British ambassador in Buenos Aires, were incredibly helpful in facilitating us obtaining information, providing their insights from the search work they had done.

"We got help with understanding how submarines work, how they are likely to behave, they really gave an incredible amount of time and insight to help us structure our search.

"It was extremely valuable. If you imagine, we were looking for an object approximately 60 metres long, lying on the ocean floor, that had suffered a catastrophic event.

Image: Ocean Infinity's ship Seabed Constructor

"So, to be able to find it needed a huge amount of input and support. Their help was truly invaluable."

He said the Navy told them to zero in on an area of about 3,000 sq km, which they then surveyed using underwater remotely-operated vehicles which map the sea bed using sonar.

It gave them 24 'targets' to look at in more detail - features on the ocean floor that could be a submarine, or could turn out to be rocks or other geological features.

The survey ship, Seabed Constructor, was just hours from giving up and going home when the 24th feature turned out to be the sub they were looking for.

Mr Plunkett, who is from Tunbridge Wells, Kent, said: "I was quietly at home.

Image: Automated Underwater Vehicles used in the hunt for the San Juan

"We have a protocol of communication. The first message goes to the Argentine naval admiral, who told the commander of the navy, who told the minister of defence, who told the president. While that was going on, I got the second phone call.

"It was a complete mix of emotions, from excitement to relief to thinking about what to do next.

"Because the careful management of that information - ultimately so that families of the crew members get to find out directly rather than seeing it on Twitter - is the single most important thing, to make sure they are treated in the most appropriate way."

He said the finding of the sub is up there with the rediscovery of the Titanic, as a technical achievement, because of its size and position.

"Not to devalue the finding of the Titanic, but the Titanic was nearly 300 metres long - five times the size of the submarine and sitting almost proud on the sea bed," he said.

"If I compare that to finding something that is one fifth the size, that looks like rocks surrounded by rocks, I think this is a tremendous achievement. And while people have found things on the sea bed before, the depth of this adds to that challenge."

The firm, which is Anglo-American with mostly British senior management and shareholders, is going on to hunt for a ship, not far from where it found the San Juan, called the Stellar Daisy, which went down in 2017 carrying iron ore while on a voyage from Brazil to China with the loss of 24 lives.

But Mr Plunkett says he also hasn't given up hope that one of the firm's other previous missions will one day be completed - Ocean Infinity was involved in the unsuccessful hunt for missing passenger jet MH370.

"We covered an area of 120,000 sq km, five times the area we have covered in this latest search, and that followed on the back of (another) search that covered 120,000 sq km," he said.

"It must be in that area of the southern Indian Ocean somewhere," he added. If people keep looking for it, "logically," he said, they will one day find it.