south indian ocean. maybe it's an consistent. i hope it is. but let's keep an open mind here. let's not build a house of cards. >> well, listen, you make a good point that all theorys are still open because investigator have made no final conclusions, just new information, taking the information as it comes. i want to thank our panel. so many difficult issues to explain to our viewers here. mary, ric, kit, and david, we'll have yor yao back to talk more in just a few minutes. but first, searching a vast, dark ocean poses a range of technical problems. we'll talk about them.