fish, they all make sounds. >> reporter: the device can pick up the pinger sounds in depthing ranging from 50,000 feet from two miles away. here's why it's so critical to get that towed pinger locater down in the deep ocean. the block box can get stuck is in something called a deep sound channel. if the sound does get trapped there and bounces around, the only way to pick it up may be through one of these pinger locater devices. >> sending the towed pinger down there, the tpl, will put you in that channel so they can hear that echoer or ricochetting sound. when it picks up the sound it's in real time sent up the cable of the boats. in real time the scientists and technicians on board the boat will be listening. >> reporter: pinger locaters have been used for years. in 1996, a tpl successfully located the black box for twa flight 800, though that was in