How on Earth do you attach a camera to a slippery devil ray?
Just one of the challenges faced by Gordon Buchanan as the series concludes.
Enter tow-cam, a lasso device which after eight hours releases the camera up to the surface.
Scientists had always thought the rays gathered in huge numbers around the Azores for a feeding frenzy, but the footage reveals an astonishing scene of pregnant females preparing to give birth.
In Turkey, cameras on brown bears help a conservation team plan for their future survival, and in France, collar-cams on sheepdogs help farmers protect their flocks.