Former Thai Navy SEAL Samarn Kunan died trying to get oxygen to the group, which just how risky getting them out would be.
Earlier, Musk had suggested a nylon tube that would inflate like a bouncy castle to form an underwater air tunnel.
Another engineer was already in the country on holiday and six more are expected to land Sunday, Weerachon Sukhontapatipak, a spokesman for Thailand's military government, said in a Saturday briefing in Bangkok.
Musk said The Boring Company's drilling capabilities might be able to help drop in battery packs and pumps from above.
Some of the kids have also indicated they can not swim and are already weak from not eating.
A video taken by Thai Navy SEALs shows the boys in the cave. The submarine would be relatively safe, even if it didn't get rigorous testing before entering service.
The boys are said to be in good health and have practised wearing diving masks and breathing in preparation for the potential complex dive. So far, explorers have not been successful with this option.
He added that the rains had stopped in the past few days, giving the rescue operation some space to make several areas in the cave dry enough for rescue workers to access. The approach would require much less power than pumping water out of the cave chambers.
An air line has been installed to the cave where the group has been trapped for almost two weeks in a chamber in the Tham Luang cave complex.
The boys became trapped in the cave two weeks ago after water rose and cut them off. They were ultimately found by rescuers 10 days after originally becoming trapped in the cave, and luckily, only "light injuries" have been reported in the group. "If Elon says it will work hopefully it will", said Bell.