Though young flatbacks have been filmed before, because of the dangerous waters they swim in, adult flatbacks have not been professionally photgraphed underwater before.

Flatbacks are only found around Australia. Here a young flatback comes to the surface to breathe.

Flatbacks come to shore to lay their eggs, as do all sea turtles.

Flatback turtles (Natator depressus) were only recognised as a separate species in 1988; before that they were classed as a type of green turtle (Chelonia mydas).

These turtles lack a pelagic phase (they don’t stay in the open ocean), preferring shallow coastal waters around the continental shelf, northern coasts of Australia, and waters south of New Guinea.

Flatbacks differ from green turtles in that they have a smooth, ‘flat-backed’ carapace (shell) with a distinctive upturned edge, allowing them to swim at speeds of up to 24km/h. Their shells can be up to 1.2m long and they can weigh up to 84kg.

As soon as they emerge, hatchling flatbacks must hurry down to the ocean, dodging birds and crabs on the way. Only a small number will make it.

Doug Perrine lugged heavycamera gear to capture the first professional underwater photographs of flatback turtles in northern WA – here a female rests on the sea bed.