The desperate effort to rescue 12 boys and their soccer coach trapped in a cave in Thailand has drawn hundreds of people, including Elon Musk, to lend their expertise, labour and hope to the task.

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In a series of tweets, the technology mogul and Tesla chief executive said his Boring Company — which digs tunnels for advanced transport systems — had advanced ground-penetrating radar, and brainstormed that an air tunnel constructed with soft tubing like a bouncy castle could provide flexible passage out.

He said engineers from The Boring Company and SpaceX companies needed to be on site to appreciate the complexities of evacuation.

A spokesperson told the BBC they were "sending SpaceX/Boring Company people from the US to Thailand today to offer support on the ground".

"Once we confirm what exactly will be helpful to send or do, we will.

"We are getting feedback and guidance from the people on the ground in Chiang Rai to determine the best way for us to assist their efforts."

The Thai Government said Mr Musk's team could help the rescue operation with location tracking, water pumping or battery power.

Tesla chief Elon Musk said he was sending engineers to help in Thailand. ( Reuters: James Glover II )

Tragically, one diver has lost his life in the rescue effort so far, and concern is also mounting that the air inside the cave may not be fit to sustain life for much longer.

It puts the prospect of drilling back in the picture, and rescue teams have thrashed their way through dense forest hundreds of metres above the cave complex, searching for an alternative way.

Western Australian drilling expert Kelvin Brown was part of the successful rescue in 2010 of 33 miners trapped 700 metres below ground in Chile, and said drilling could be used to get the boys out, but there were variables — and also risks.

A military transport helicopter carries a drill machine that could help rescue the boys. ( AP: Sakchai Lalit )

Soft rock an advantage

There are some slight differences between drilling into a mine and a tourist cave — availability of information being one of them.

Mr Brown was able to study data about previous drilling at the Chilean mine to determine how the rigs were going to behave.

"We knew what the formation was, we knew if there were faulted zones, the presence of aquafers," he he told PM.

"I'm not too sure all that information is actually at hand in this Thai scenario.

"But it's all possible, as was proven."

In Thailand, Mr Brown said he thought there was one aspect working in favour of drilling — the softer rock.

"It's most probably some form of limestone, which to a driller is absolute butter and is extremely quick to drill through," he said.

By comparison, the rock at the mine in Chile was volcanic and extremely hard, which caused the drills to deviate.

"But I would expect that in Thailand it would be extremely soft and should be quite quick to drill."

Sorry, this video has expired Thai boys in high spirits as rescuers plan next move.

There is, however, a problem.

"As a driller, I drill to targets; obviously I have to know where that is in space," he said.

"So, I have X, Y and Z — three-dimensional coordinates.

"I'm not too sure they have those, but that would be a must-have."

If those coordinates were known, he said he believed drilling directly to the target zone — where the team is waiting — would be the best option.

"Going to a water-filled cavity probably makes no sense, so I'm assuming you would try to drill directly where they are in an air pocket."

Additional holes could also be drilled to aid the rescue effort.

At the mine in Chile, three holes were drilled: one for food and supplies; a second for communication; and a third to pull the miners out.

"So it makes a bit more sense to me anyway, at least for the sake of safe access, to use a drill hole."

A map shared by a Thai diving website demonstrates the difficult conditions diving rescuers would face. ( Facebook: Digitalay )

How long would it take?

"Doing a double shift, which is drilling two 12-hour shifts — so 24 hours — it really depends on the method, and that will be dictated by the logistics — if you can physically get the right equipment in," Mr Brown said.

He said diamond drilling was common in the region, and that meant it should not be difficult to get a drilling rig into the area at short notice.

But he said while the diamond drill took less power and space, it was also slower than the alternatives.

"That could probably get there anywhere from 10 days, maybe a little bit less because of the limestone being softer," he said.

"The more high-powered rigs, which is what we used in Chile, probably three days."

With the monsoon rains imminent, Mr Brown said he hoped the drilling option was being considered.

International rescuers are hoping to evacuate at least some of the boys before heavy rains hit. ( AP: Sakchai Lalit )

What could go wrong?

Well, it depends on the drilling techniques used.

For one thing, high-pressure air drills are extremely loud.

"You don't want to be in the vicinity when the hammer breaks through," Mr Brown said.

Then there is diamond drilling, which uses a huge column of water and diamond-impregnated drill bits.

"And if it is 1,000 metres of water, that's a very high head of pressure," he said.

"As soon as you break through, that 1km column of water instantly wants to enter into the area.

"So, there most certainly would be some risk if we intersected exactly where they are."

And beyond extreme noise and water pressure, there is the possibility of the people trapped in the cave being hit by rocks.

"If you dislodged the formation — and that's another thing that we don't know too much about the geology: is it unstable, is it fractured — you may actually dislodge boulders as you approach and break through.

"So, there is certainly some risk to that approach."

But Mr Brown said he believed the approach was worth trying.

"To me it looks like a long section that they have available to them," he said.

"You could certainly have, as we did in Copiapo, you could have multiple drills all targeting different areas.

"Certainly in light of what happened in Chile, it's proven it can happen."

Sorry, this video has expired Expert in disaster mental health Sarb Johal says the boys' morale is heartening.

ABC/AP