they won't hear any more pings. so they have a relatively small area that this sub messible has to go back and forth to try to find some wreckage. >> they'll send the av down. in order to take sonar images of the bottom, you have to get close to the bottom. that's a fact. the av will drive down there and run a pattern. and it's limited. it's 16 square miles a day plus or minus. that's not exact. that's if everything works perfect. because two hours down, two hours back, four hours of downloading data, changing batteries, reprogramming the system, firing up the -- >> so this could take a few weeks at least. >> yes, every dive -- >> if they're lucky. >> exactly. the system is designed to come back. if it hits a problem, a depth it's not supposed to or hits something that tells it stop, come back up, it's not safe, it will come back up. the 16 hours could be 8 hours, 4 hours. it's not rocket science, but it