Elon Musk unveils 'kid-size' submarine for Thai cave rescue

The world is captivated by the plight of a Thai soccer team trapped in a flooded cave - and so, too, is billionaire inventor Elon Musk

As rescuers began a daring extraction of the boys and their coach from the cave over the weekend, Musk said he had sent a "child-size submarine" to the country to assist in the massive rescue effort.

"Hopefully useful," he wrote in one tweet, noting that the device would arrive in 17 hours. "If not, perhaps it will be in a future situation."

Hours later, Musk shared video of the narrow, bullet-shaped tube being maneuvered through an underwater obstacle course with the assistance of two divers.

The exercise, Musk noted, was an attempt to simulate moving through a narrow passage.

Eight boys have been removed from the cave by a team of Thai and international divers. Four more boys and the 25-year-old coach remain inside the cave, where they have been trapped for more than two weeks.

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The rescued boys - whose conditions remain unknown - were brought by helicopter to a hospital in Chiang Rai.

Crews are rushing to rescue the boys before the cave complex is inundated again by seasonal rains.

Musk has been tweeting about the rescue effort for days and said he is "amazed by the bravery, resilience & tenacity of kids & diving team in Thailand."

"Human character at its best," he added.

He also tweeted that SpaceX and Boring Co. engineers were headed to Thailand to see whether they could assist Thai authorities. After noting that he'd been consulting with cave experts in Thailand over the weekend, the Tesla CEO began tweeting about the specifics of the "escape pod" his team was developing.

For the pod's hull, he said, designers used a "liquid oxygen transfer tube" from SpaceX's Falcon rocket. Testers strapped weight belts around the outside of the pod and Musk noted that the tube was light enough (about 88 pounds) to be carried across dry sections of the cave.

Musk hasn't revealed whether his engineers have arrived on the ground in Thailand or been able to assist in the precarious rescue effort. That effort has already cost one rescuer his life.

Thai Navy Sgt. Saman Kunan, an ex-SEAL, died Friday from a lack of oxygen as he attempted to place air tanks inside the cave complex.