Elon Musk unveils ‘kid-size’ submarine for Thai cave rescue -- The Washington Post

Repurposing a SpaceX liquid oxygen transfer tube; also see Elon Musk's submarine 'not practical' for Thai cave mission, rescue head says (CNET)

"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 “kid-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.”"

Elon Musk unveils ‘kid-size’ submarine for Thai cave rescue -- The Washington Post