Unsworth said Monday that he is considering legal action against Musk, telling a reporter for Australia's Nine Network, "it's not finished."
Asked how he felt about Musk's remark, Unsworth added: "I am not gonna make any further comment about him but I think people realize what sort of a guy he is."
The experienced caver whose knowledge of the Tham Luang cave system helped pinpoint the boys location had said in an earlier interview with CNN that Musk's miniature escape pod "had absolutely no chance of working."
He can "stick his submarine where it hurts," Unsworth said during the interview in Thailand.
Musk posted the baseless accusation shortly after.
When Twitter users called out Musk's attack on Unsworth as unfair, he doubled down.
"Bet ya a signed dollar it's true," he wrote in another tweet that has since been removed.
Representatives for Musk and his companies — SpaceX, Boring Co. and Tesla — did not respond to requests for comment Sunday.
Musk, who's not shy about courting controversy on social media, draws intense attention to each post he makes.
In the midst of the tense rescue mission earlier this month, Musk announced plans to help. He proceeded to post regular updates on social media, including photos and a video of a "kid-size" submarine being constructed and tested.
"Hopefully useful," he said in one tweet. "If not, perhaps it will be in a future situation."
Ultimately, the capsule was not used in the rescue mission, and it was criticized by some as a distraction. The mission commander, Narongsak Osotthanakorn, said at one point that the submarine "doesn't fit with our mission," according to the BBC.
That prompted a retort from Musk. He responded to a tweet from the BBC, saying Osotthanakorn was "not the subject matter expert."
