Musk proposes mini-subs to save boys stuck in Thai cave

American tech entrepreneur Elon Musk has proposed a mini-submarine to save the boys trapped inside a flooded Thai cave, floating the idea on social media while linking it to his space exploration business.

After garnering headlines with initial ideas of installing a giant air tube inside the cave complex and using his firm's penetrating radar to dig holes to reach the boys, Musk's latest concept is the pod.

"Primary path is basically a tiny, kid-size submarine using the liquid oxygen transfer tube of Falcon rocket as hull," Musk said in a tweet to his 22 million followers. "Light enough to be carried by 2 divers, small enough to get through narrow gaps. Extremely robust."

An accompanying video of people testing the submarine in a swimming pool in Los Angeles that was posted overnight yesterday attracted more than 3.1 million views in 10 hours.

Many people offered positive comments, with fans hailing Musk and his engineers for their creativity. Other people, however, questioned whether Musk's plan was credible.

"Seriously? No kid or adult will want to be in there for any amount of time. Rethink this. CAT or open MRI machines create unsurmountable anxiety. Go back to the drawing board," one person wrote to Musk on Twitter.

The mini-submarine is due to arrive in Thailand today, Musk wrote.

Last week Musk said he was sending teams to Thailand from his private space exploration firm, SpaceX, and engineering firm, Boring Co, which is developing tunnelling systems for transport projects.

While offering the mini-submarine as a potential saviour, Musk again used the opportunity to promote space exploration. "With some mods, this could also work as an escape pod in space," Musk said on Twitter.

Thai authorities have said they are welcoming all offers of help in the rescue effort for the boys, who became trapped in a complex cave system in mountainous northern Thailand on June 23 when rising waters hemmed them in.

Twelve boys aged from 11 to 16, plus their 25-year-old coach, were caught inside the cave. Elite divers began a rescue mission yesterday, successfully escorting four of them out, and were aiming to extract the others swiftly before fresh monsoon rains made escape impossible.