Heard a theory they might put the kids one by one into a sealed water tight torpedo/coffin type container with oxygen and pull or push them out,make it the size of the tallest kid and then you know they'll all fit in it.
Sounds plausible until you consider how to adjust the buoyancy of the capsule and the non linear tunnels. The media can`t even describe the masks properly, they`re not OXYGEN masks , they`re just full fave diving masks. Divers don`t breathe oxygen generally, it`s just compressed air. Oxygen /Nitrox is used for decompression stops. (Special Forces use Oxygen Rebreathers ,LAR Vs and other mixed gas RBs )