A British diver who helped rescue 12 Thai boys from a flooded cave has criticised Elon Musk's plan to retrieve them using a mini-submarine, calling it a "PR stunt".

"He can stick his submarine where it hurts," said Vern Unsworth, 63, a Briton who lives in Thailand.

Rolling his eyes Mr Unsworth told CNN: "It just had absolutely no chance of working. They had no conception of what the cave passage was like.

"The submarine, I believe was about 5ft 6 long, rigid, so it wouldn't have gone round corners or any obstacles. It wouldn't have made the first 50 metres into the cave from the dive start point. Just a PR stunt."

Mr Musk had himself gone into the cave, but Mr Unsworh said: "...and was asked to leave very quickly, and so he should have been."