A routine drone survey turns deadly when Ryan Johnson, a marine biologist based in South Africa, films a humpback whale being attacked and strategically drowned by a Great white shark. This is a total perspective shift on a creature he's spent his life studying. To make sense of this event, Ryan follows Humpback whales on their migration, mapping their weak spots. He also takes a new look at Great White sharks. How do they become whale killers? —National Geographic