The Tesla boss sent a profanity-laden tirade to a reporter in which he baselessly suggested that Mr Unsworth had a "child bride".
Mr Musk has repeatedly and without any evidence at all claimed that Mr Unsworth is a paedophile and that people around the rescue did not like him. The abuse has apparently come from Mr Musk because he was upset that Mr Unsworth had mocked his attempts to get involved with the mission, which involved a special diving capsule that was widely derided as useless.
Mr Musk initially apologised for his first messages, in which he referred to the diver as "pedo guy". But he continues to revive the allegation, including in his latest and most intense comments.
Asked about legal threats from Mr Unsworth's lawyer over the allegations, Mr Musk continued to double down on the attacks.
"I suggest that you call people you know in Thailand, find out what’s actually going on and stop defending child rapists, you f***ing asshole," he said in the email to BuzzFeed reporter Ryan Mac, who posted the message in full on Twitter. "He’s an old, single white guy from England who’s been travelling to or living in Thailand for 30 to 40 years, mostly Pattaya Beach, until moving to Chiang Rai for a child bride who was about 12 years old at the time."
He signed off with a message about the lingering threat of the lawsuit. "As for this alleged threat of a lawsuit, which magically appeared when I raised the issue (nothing was sent or raised beforehand), I f***ing hope he sues me."
He then sent a follow-up message in which he continued to defend his "mini-sub" – the capsule he had instructed his employees to make but which was rejected by diving teams on the ground. He claimed that it would have worked and that it was going to be tried, despite suggestions from some experts that it would not have been able to fit through the cave system.
Mr Musk's latest attacks on Mr Unsworth began in the wake of a New York Times interview in which he repeatedly broke down while revealing the toll working so hard at Tesla was taking on him. He revealed that he sometimes came to regret his late night posts, and that the company's board was concerned about the damage his outbursts were doing.