SINGAPORE: Tech billionaire Elon Musk has defended the "kid-size" submarine he had proposed to rescue the 12 schoolboys and their football coach formerly trapped in Thailand's Tham Luang cave complex.
He also questioned the authority of Thai rescue chief Narongsak Osottanakorn although the trapped "Wild Boar" football team were successfully brought out of the cave on Tuesday.
The CEO of aerospace manufacturer SpaceX created a lot of hype over the submarine, mainly on his Twitter account, where he has more than 20 million followers.
The submarine, Mr Musk had said, uses liquid oxygen and is light enough to be carried by two divers and small enough to fit through narrow gaps.
"Extremely robust," tweeted the 47-year-old, who left the submarine at Tham Luang on Monday in case the rescue team needed it.
However, the three-day rescue operation that concluded on Tuesday had left the submarine unused.
"It doesn't fit with our mission to go in the cave," rescue operations chief Narongsak told reporters on Tuesday, according to BBC.
Mr Musk reacted by tweeting what appears to be an email correspondence between him and Mr Richard Stanton, one of the British cave divers who found the missing football team in the Tham Luang cave complex nine days after they went missing on Jun 23.
The email correspondence showed encouragement from Mr Stanton, 56, to "keep working" on the submarine.
"We're worried about the smallest lad please keep working on the capsule details," he had said.
Mr Musk replied: "Sounds good, will continue. Parts are being assembled and will undergo testing in a water in a few hours ... Operating principle is the same as spacecraft design - no loss of life even with two failures."
Mr Musk had also disputed the title of the head of rescue operations, saying that Mr Narongsak was described inaccurately as "rescue chief" and was "not the subject matter expert".
READ MORE | Full coverage of the search and rescue operation: https://www.channelnewsasia.com/news/topic/Thailand-cave-rescue