jacques coustea. you know some things about the deep ocean. it's proving to be quite a mystery to us. we see an example of that in the plane. let's start with the ferry. we see this ongoing search effort. it's not a recovery, they're treating it like a search and rescue still. give us an idea of some of the challenges those divers are facing with an upturned ferry. >> it's a really difficult situation. the positive news is that there's a good chance of still recovering some survivors. but for a diver, you have to remember when you penetrate that structure from down below, it's pitch dark in there. you're maneuvering around a maze. if you're going to try and extract people from the hull itself, from the surface, you potentially endanger those people that you're trying to rescue, because the water goes into that compartment that presumably has air and unfortunately you might have a situation on your hands. >> you're saying there's a good chance survivors thinking they were perhaps able to find a void