The youth soccer team, aged between 11-15, went missing on June 23 along with their 25-year-old coach.
Musk said in a tweet Sunday evening that the pod -- or "kid-size submarine" -- was en route to Thailand and would arrive in about 17 hours. They've already been trapped for two weeks. The rescue efforts involve resources from UK, USA, and local teams as well.
Responding to a question on Twitter, the entrepreneur and engineering mastermind said "divers who have made the passage", believe the pod is small enough to fit through the most narrow portions of the cave. Musk said they were being tested Friday afternoon in a pool with a subject who had never been scuba diving. The tweets show the submarine being slowly ferried underwater by a team of divers.
Though rescuers found the group after nine days and they have received food, blankets and medical attention, it is still a risky dive and scramble through four kilometres of tunnels where they are trapped in - as they can not swim or dive.
Some of the kids have also indicated they can not swim and are already weak from not eating.
"Also building an inflatable tube with airlocks", he wrote.
Initial elation at finding 12 boys and their soccer coach in a Thai cave has since turned to concern at not being able to immediately extract them, and sadness after a diver bringing supplies died during his exit. Officials are also concerned that rain in coming days could flood the spot where the team is located.
The group entered the cave system when it was try, but subsequent heavy rain has meant that the way out has flooded.
Teams of Thai and worldwide divers have since supplied them with food, oxygen and medical attention, but there are mounting concerns about the oxygen level in the chamber, which officials said had fallen to 15%.
"Now and in the next three or four days, the conditions are flawless in terms of the water, the weather and the boys' health", he told reporters this afternoon.