they got through in very quick time, which means they obviously had minimal problems so they obviously went very quickly. and they were given the basic concepts of how to breathe underwater, what to do and not to do. extremely difficult. very scary and very dramatic. >> we can never underscore enough the fact that these teams that are on the ground in thailand and certainly international support that's joined in. these people are putting their lives on the line as well. we saw that former thai navy s.e.a.l. lose his life of course in this operation. how dangerous is this? i mean, certainly so far so good. that's the resounding feeling around the world, that the four have been rescued so far. but how dangerous is this technical dive? the traversing of this cave system for these brave members of this team. >> it is extremely dangerous. you can't underestimate how