A fully grown leatherback turtle can measure over two metres from head to tail and weigh as much as 900 kilograms - heavier than a small car. Despite this size, they are graceful swimmers and can dive deeper than 1,000 metres. They feed almost entirely on jellyfish, and can eat over 100 kilograms of jellyfish in a single day.
Female leatherbacks come ashore at night to lay their eggs, usually returning to the exact beach where they were born many years earlier. Scientists believe they use the Earth's magnetic field - a bit like a built-in compass - to navigate thousands of kilometres across the ocean and find the right beach. The journey from feeding grounds in the Atlantic back to Bioko can be over 7,000 kilometres.
On Bioko's beaches, a female leatherback digs a deep hole in the sand with her back flippers, lays around 80 to 100 eggs the size of billiard balls, covers them carefully, then returns to the sea. The eggs hatch after about two months, and tiny hatchlings no bigger than a matchbox scramble toward the ocean. The beach is one of the most magical places in Equatorial Guinea on a hatching night.
Leatherbacks have lived on Earth for over 90 million years - they swam in the same oceans as the dinosaurs. Protecting nesting beaches like those on Bioko is vital because these turtles need undisturbed sand and dark skies to find their way. Local communities and conservation teams on Bioko work together each season to keep the beaches safe.