Elon Musk's tiny submarine is headed for the Thai caves - but it may not make it in time to help

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• Elon Musk has offered his assistance and floated plans to save the soccer team stranded in a Thai cave network.
• He said he sent a mini-submarine to Thailand, which is expected to arrive Monday night local time.
• However, rescue efforts are already underway and may be over by the time Musk's submarine arrives.

A tiny submarine is on its way to Thailand, sent by Tesla CEO Elon Musk to help rescue the remaining members of a youth soccer team who are trapped in a cave. 

On Sunday night, Must tweeted that the mini-submarine would arrive around 11 p.m. on Monday Thailand time. However, this may be too late to be of use in the rescue mission.

"Mini-sub arriving in about 17 hours. Hopefully useful. If not, perhaps it will be in a future situation," he wrote.

Rescue divers extracted four boys from the cave on Sunday and headed back on Monday to rescue the remaining eight and their soccer coach.

Thai officials say the  rescue operation is estimated to take 10 hours and end by 9 p.m. on Monday. Early reports suggest that it may progress even faster.

The four boys who were rescued on Sunday had to travel about 2.5 miles with oxygen tanks. They made their way back to the cave's entrance using a 3-mile rope. They were accompanied by two divers throughout.

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After Musk received an outpouring of gratitude for his rescue plans, he replied: "Thanks, we've not done anything useful yet. It is all other people."

The billionaire entrepreneur has been tweeting proposals and offering his services to the Thai government in their efforts to extract 12 boys and their soccer coach from a partially flooded cave.

The group had been stranded there since June 23.

On July 8, he tweeted videos of his engineers testing a "kid-sized submarine" underwater in Los Angeles - which is now on its way to Thailand.

Last Friday, Musk suggested inserting a tube or series of tubes through the Tham Luang cave network and inflating them, creating a tunnel for the boys to travel through without needing to scuba dive.

He added that engineers from two of his companies, SpaceX and the Boring Company, were travelling to Thailand to offer assistance.

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An ambulance carrying one of the boys rescued from the Tham Luang cave on Sunday.