The only sea turtle that breeds nowhere but Australia, with a low domed shell and upturned shell margins. Rarely seen on reef.
Shell 76 to 96 cm and usually 70 to 90 kg. The shell is the flattest of any sea turtle and its edges turn up, which is the quickest way to know one. Pale olive green to grey above, cream below, with four pairs of costal scutes and a single pair of scales between the eyes. The shell is unusually thin and waxy and scratches easily.
The green turtle has the same scute counts and is the real confusion. The flatback is flatter, its shell margins turn up, and it is pale grey-olive with a waxy surface where the green turtle is more domed and harder. The olive ridley is separated at once by its five to nine costal scutes and two pairs of scales between the eyes.
It feeds on the bottom on soft corals, sea pens, sea cucumbers, jellyfish and molluscs, over mud and sand rather than coral, and it does not rest under reef ledges the way green and hawksbill turtles do. It is a shelf animal, almost always in less than 60 m, and it is the only sea turtle with no open-ocean juvenile phase.
It nests nowhere in the world except Australia, but it is a turbid inshore species and is uncommon to rare on the outer Great Barrier Reef where most diving happens. Realistic sightings are in shallow inshore water in the Gulf of Carpentaria, Torres Strait, the Kimberley and inshore Cape York. The IUCN lists it as data deficient, which means there is not enough information to assess it rather than that it is secure.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.