Conditions were so unsafe that a retired Thai Navy SEAL died on Friday while trying to lay out oxygen tanks underwater in a tunnel, and the rescue chief at one point dubbed the operation "Mission Impossible".
After more than two weeks trapped in a cave, all 12 members of the Wild Boars football team and their coach have been rescued.
The remaining four boys and their 25-year-old coach remain in the cave, with highly-anticipated rescue efforts underway.
The eight boys brought out on Sunday and Monday were in good health overall and some asked for chocolate bread for breakfast, officials said earlier.
The boys and their coach, all from the "Wild Boars" soccer team, became trapped by rainy season floodwater on June 23rd when they had set out to explore the vast cave complex after soccer practice.
The boys and their coach have now all been taken to hospital after the three-day evacuation that was a battle against heavy, predicted rain.
At a news conference, Jedsada Chokdumrongsuk, permanent secretary at the Public Health Ministry, said the first four boys rescued, aged 12 to 16, are now able to eat normal food, though they can't yet take the spicy dishes favoured by many Thais.
"We will look into finding a new opportunity to invite the boys to a Federation Internationale de Football Association event to share with them a moment of communion and celebration", Federation Internationale de Football Association said in a statement. Last Friday, one former Thai Navy Seal died while placing oxygen tanks deep within the caves.
"We are not sure if this is a miracle, a science, or what", read the post on the official Thai Navy SEAL Facebook page this morning.
There are concerns they may have consumed contaminated water, while bird or bat droppings could cause infections. The boys and their coach have to spend time in isolation to protect against the spread of any possible infections they may have contracted while in the cave.
"I hope today we will be faster or the same speed as yesterday", Narongsak said.
They're all likely to stay the hospital for seven days due to their weakened immune systems, Chokedamrongsook said.
Musk said the submarine, which is made from the liquid oxygen tube of SpaceX's Falcon rocket, is small enough to fit through the cave system's narrow passageways.