. >> what follows next is a sort of choreographed underwate undee ball ballet.nd, holding on to the rope, and the other holding tight to the strap on the boy's vest as he floats face-down. >> it's like an underwater obstacle course, where you're blind. >> he's halfway home, in complete darkness, when the unthinkable happens. the boy starts to wake up. you realize you've got to ster . >> it was tricky. >> you're grabbing the stuff in the water, trying to put it back in. >> and trying to get the needle on the syringe. >> had you ever given a shot before? >> never. the responsibility was huge. >> meanwhile, in chamber three, a group of thai navy s.e.a.l.s anxiously awaiting. >> until the line started to move, we had no idea. it was more nerve-racking when they said, the line the moving. 5 to 10 minutes later, somebody is coming up. >> then he emerges from the darkness. >> everybody w worked. >> the doctor measured the oxygen level in the body. >> he's then loaded on to a stretcher for the remaining half-mile extraction. >> but it won't be easy. they have to navigat