Icy Killers: Secrets of Alaska's Salmon Sharks

It's one of nature's greatest spectacles and it happens once a year in the frigid waters of Alaska's Prince William Sound. It is a predestined collision of two massive migrations - a David and Goliath event - when thousands of ravenous salmon sharks gather to attack millions of Pacific salmon. These warm-blooded sharks can weigh up to 500 pounds and grow up to 9 feet long. They are the fastest predators in these Alaskan waters and their ravenous appetite makes them deadly to salmon.