that was in water, i think about 13,000 feet deep. my understanding, the water in this area is only 296 feet deep. in terms of the black box, that has actual sonar device, it sends out a signal, doesn't it? >> yes, the flight data recorder and the cockpit voice recorder would have acoustic beacons that operate on a battery power about 30 days. and they should be sending out pings that would be audible to vessels that have under water listening devices. of course, that's assuming they're functioning and not buried in the mud of the sea floor or buried in the aircraft wreckage and assumes that the vessels that are listening are in the range of the acoustic beacon. >> how far away can they be? >> i think it depends on the conditions in the ocean, how deep it is, and whether there's a thermal layer, temperature gradient that might channel the acoustic signal away from the