Underwater Obstructions News Today

Them so divers dont get hurt. >> underwater obstructions are a concern. we tend to fly the auv at about a 45-meter altitude of the bottom. keeps us usually out of the way of obstructions. >> reporter: these types of searches can take months or years. but the payoff is high. wreckage that gives clues about what happened, data recorders and the thing that matters most, the fate of the people on board. rosa flores, cnn, new york. >> so thats an idea of how its going out there. but right now, chad m...

>> the smaller ones are only going to down to 5,000 feet. the next is a larger device thats 15 by 25 feet. its very large because it adds a lot of battery capability and hydraulics capability. >> reporter: the auvs can go as deep as 20,000 feet sending acoustic pulses to the sea floor to find debris and then maps are drawn to guide search teams. they can even find things up to 300 feet under the sea floor. the search zone needs to be narrowed down first. this auv can only search eight square mil...