A British diver involved in rescuing a Thai boy’s soccer team from a submerged cave has a low opinion of Tesla CEO Elon Musk’s very public offers of help, telling CNN that Musk “can stick his submarine where it hurts.”
Musk’s proposal to rescue the team with a small submarine “just had absolutely no chance of working,” said diver Vern Unsworth, who played a major role in the rescue. “[Musk] had no conception of what the cave passage was like. The submarine, I believe, was about 5 foot 6 long, rigid, so it wouldn’t have gone round corners or round any obstacles.”
“It wouldn’t have made the first 50 meters into the cave from the dive start point,” Unsworth continued. “Just a PR stunt.”
Musk on July 6 began brainstorming at length on Twitter about a small submarine to help rescue the team. The sub was quickly built and tested using SpaceX components and engineers, with the process extensively documented and shared by Musk.
But the team was extricated by Tuesday, July 10, without the device. Thai authorities said the sub was “not practical,” a point Unsworth was happy to expand on.
“It just had absolutely no chance of working,” he continued.
Get Data Sheet, Fortune’s technology newsletter.
And Unsworth should know – he was instrumental in the boys’ rescue, convincing Thai authorities to call on a team of English divers who knew the cave, according to the Daily Mail. Unsworth’s knowledge of the Tham Luang cave, gleaned over what he says has been six years of exploration, helped locate the missing boys.
Musk’s offer of help with the crisis has proven polarizing. Though many saw the effort as good-hearted, some shared Unsworth’s cynicism, accusing Musk of egotism, overconfidence, and self-aggrandizement.
Musk seems to have been well aware of the blowback, writing that the criticism “has shaken my opinion of many people.”
Musk has also defended himself from skeptics of the subs’ potential usefulness, sharing correspondence with the rescue team as they provided encouragement and feedback.
The Thai Navy has since said it may use the submarine at some point in the future, but if Unsworth is to be believed, it won’t be for tricky cave rescues.