rod mccallum has extensive experience searching under water. rob is here with us right now. so how difficult of a mission is this, since they're not even sure, as i've been saying, they're looking in the right place? but now all of this high-tech underwater equipment has been put in place, and it's moving around. trying to hear that pinger. >> yeah. it is a long shot. but although it's a long shot, it's the best shot. you know, there's no sense in having those assets in that part of the world and not having them in the water actually searching. so, you know, they're using the best data they can from the last known tracker, and they are deploying the assets along that track. and it's a shot in the dark, but it's an informed one. >> and it's basically, you know -- it includes a lot of luck. because that equipment can only move in a relatively tiny area every day. >> that's right. it's essentially a microphone, an underwater microphone, hydro phone, with very limited range, perhaps a couple of miles.