is it a surprise to you this bluefin-21 reached its underwater depth? >> not a surprise to me, anderson. they are operating right the edge of their operating capability. much of the sea floor is at that depth, 4,500 meters. if they come in a little bit to the south they will be on the flank of an underwater plateau. more rugged. to the north deeper still. they have the maps. i don't know what the accuracy of the maps they have. >> if they seem to be caught by surprise by this trench or depth does it indicate that they don't have a real good scene of the floor? >> well it's tough to get that kind of detail when you come down the operations of a vehicle. you get some general sense. you heard angus houston talk about gentle rolling terrain. inside that rolling terrain