there could have been crevices, gullies, that type of thing very easily. the fact they are tracking the terrain so keeping 30 meters above the sea floor. if the sea floor takes a dive so does the vehicle. that's where they got in trouble. >> there's a crush depth for the vehicle. it goes too depth the pressure -- >> my understanding is that 4,500 is comfortable operating depth and that they could get down to 4900 before the vehicle actually implodes. >> it does raise a question whether they will be experiencing this kind of aborted mission frequently. . >> it does. i don't know if david knew about how deep it was but what i heard him say also is the programming of it. what worries me about that what other programming things have to be reset when it comes back up. we were talk being before about doing 18 square miles a day. at this rate no way they will get that. >> mary, what do you make of this oil slick or what they believe to be an oil slick that