The sea creatures have outlived the dinosaurs, but they're now threatened by fishermen.
They get caught up in the nets used to catch tuna and swordfish and they die, scientists said.
It's thought the number of these turtles has dropped by 95 per cent in the last few decades.
Thick, leathery shells
Leatherback turtles are the largest and oldest sea reptile in the world.
They've been around for more than 100 million years, and have survived asteroids and huge changes to the planet.
Scientists are calling on people to stop eating swordfish particularly, until something's done to change fishing methods to save the turtles.