CHIANG RAI, Thailand -- It's been more than a week since 12 boys and their soccer coach got trapped inside a flooded cave. Rescue crews have brought them food and medicine, but it's still too dangerous to bring them out.

Video of the boys from inside the cave shows them flashing peace signs and smiling. One by one, they look at the camera and say they're in good health.

But outside the cave, rescuers are struggling to come up with a plan to bring the boys out safely. The local governor says the children are being given a crash course in swimming. They have tried on dive masks that would allow them to breathe underwater if rescuers decide to attempt what would be a very dangerous and long swim through a dark and narrow cave.

Boys from a youth soccer team trapped inside Tham Luang cave covered in hypothermia blankets react to the camera in Chiang Rai, Thailand, in this still image taken from a July 3, 2018 video by Thai Navy SEAL. Thai Navy Seal/Handout via Reuters TV / REUTERS

"If you don't know how to swim and you are in very black environment that could potentially kill you inside a cave, it's not a good environment to learn in," said Claus Rasmusen, a volunteer cave diver.

In the meantime, crews are trying to pump as much water as possible out of the cave. The hope is that they can bring the water level down, so that it's safer for the kids to escape.

Rescue crews have also been staging rehearsals for how they would remove the boys by ambulance from the scene after they emerge. However, there are concerns about more flooding this weekend, when monsoon rains are supposed to return, so two places where rain can enter the cave have been blocked up.