$2.5 million. mike purcell is the principle engineer here. >> they can go up and down mountains that are up to 40 degrees in slope. they are very stable, so you get really good data almost all of the time. >> reporter: why would this underwater robot find something even the u.s. navy and search teams from more than two dozen different countries haven't been able to find? first of all, the torpedo-shaped vehicle can reach depths of up to 6,000 meters or more than three-and-a-half miles below the surface. and it can survey water swaths of the ocean floor using what's called side scan s.o.n.a.r. >> they send a sound pulse that's sort of a fan beam out to the side, and it will it travel out almost half a mile from the vehicle. and it bounces off the sea floor, and we get a reflection back to the vehicle. >> reporter: they call the process mowing the lawn, because it works its assigned grid back and forth before returning to the surface with images. captured on a high-resolution camera. it's all done at the touch of a