Leatherback sea turtles are one of the ocean's most mysterious creatures. These endangered turtles travel thousands of miles each year, from the tropics to cool northern waters to feed on jellyfish. Yet despite their enormous size and worldwide distribution, we know little about their day-to-day lives in the ocean, including where, when, and how they feed. Studying these enigmatic turtles at sea is not easy, because they spend most of their time underwater. The technology to follow and image them in open water has not been available—until now.