dr. ryan johnson and about the only animals that spend more time cruising these waters are the great whites that thrive in this part of south africa. since making it hisk to demyself if i these monsters, he's gone diving with them countless times. he's used bite meters to measure the strength of their jaws. >> end of that experiment tonight. >> reporter: and even developed silicon robo-seals to study the way great whites hunt in this part of the world. >> oh, he's got it! >> reporter: in fact, this experiment was almost too successful. the sharks were so convinced in robo-seems authenticity than began ripping them to this reds. but not before ryan made a breakthrough discovery. though most sharks don't hunt at night, the great whites taught themselves to use the light from the shore to grab seals in the pitch blackness. and with thermal cameras, he captured the first recorded instance of a night hunt. >> you did it! it's just gone on 7:20 at night. i just heard the breach. these animals are incredible. >> reporter: but of course, these animals also enjoy snacking in the sunshine. so, ryan g

dr. ryan johnson is the marine biologist behind this idea, and by sight and name -- he knows the great whites of mossel bay better than anyone. he's used robotic seals to prove that they use light from the shore to hunt at night. and he's even had a shark accidentally jump into his boat. but he's also seen how these predators behave themselves less than a half mile from some of the most popular beaches in africa. there hasn't been an attack here in 20 years, and among many locals, "galeophobia" has gradually faded. aren't you at all worried that one nibble could set all this back and reinstill all that fear? >> yeah, it's something we live with all the time. a shark attack or shark bite is tragic for shark conservation. >> reporter: and so friday night, he will send his shark angels into the water, on live television, befting their limbs and his reputation that the creature of our night mares is simply misunderstood. bill weir, abc news, in mossel bay, south africa. >> and there will be more reporting from bill later on "nightline." and "shark attack" will air on friday on gnat gnat geo wild.

dr. ryan johnson is the marine biologist behind the idea and by sight and name he knows the great whiteser than any one. he has used robotic seals to prove that they use light from the shore to hunt at night. he even had a shark accidentally jump into his boat. he has also seen how the predators behave themselves less than a half mile from some of the most popular beaches in africa. aren't you at all worryd that one anybodile could set it all this back -- nibble could set tall week and rein still the fear? >> a shark attack is tragic for shark conservation. >> friday night he will send his shark angels back in the water on live television. bill weir, in south africa. >> well, work a wave of his hand, president obama gave two plump turkeys a thanksgiving reprieve. liberty sat calmly as the president and his daughters offered a blessing. another turkey named peace was also spare. >> tomorrow is one of the best days of the year to be an american. it is a day to count our blessings, spend time with the ones we love and enjoy some good food and some great company. but it is also one of the wo