He has now designed a plan to help save the boys, and he said engineers from his companies would travel to Thailand on Saturday.
The struggle to bring the 12 boys and their coach to safety is growing increasingly perilous.
Last year, after a devastating hurricane hit Puerto Rico, the government there asked Mr Musk for help.
Musk acknowledged there are many complexities to the rescue mission, he has begun brainstorming some ideas that involve inserting a one-metre nylon tube through the cave network and inflating it with air like a "bouncy castle".
Most of the boys can not swim. Heavy rains are forecast for this Sunday, and the boys are now being trained in the use of scuba diving gear while the Thai Navy Seals prepare the 5km-long route for their anticipated evacuation. The submarine would be relatively safe, even if it didn't get rigorous testing before entering service. So far, explorers have not been successful with this option.
Trump to avoid London protests with tour of English country homes
Johnson said, referring to the prime minister's ceremonial country estate in Ellesborough, about 45 miles northwest of London. Trump's wife, Melania, will have a separate itinerary and will be hosted by May's husband Philip.
"We are racing against the rain", the coordinator of this rescue operation said yesterday.
Things are getting desperate for the 12 boys and their football coach, who have been underground since June 23. Rescuers are scrambling to lower water levels with pumps and prepare the group for a perilous, hours-long extraction that would include diving through pitch-black water with scuba gear.
Authorities are anxious about a worst-case scenario where heavy downpour for an extended period in the area could lead to complete flooding inside the cave, including the area now occupied by the boys and more than 10 Navy SEAL members.
Among his tweets about the rescue, he also said: "But let's not submit to the bad mood entirely".
Monsoon flooding cut off their escape and prevented rescuers from finding them for nine days.