Marcel Gubern's Image

Sipadan Island, off the east coast of Sabah, Borneo, is renowned for its relatively pristine coral reefs and rich marine life.

It's a hotspot for sea turtles, which gather there to mate and nest. And it was turtles that Marcel was after. As he returned to his boat at the end of the very last dive of his trip, Marcel noticed a green turtle floating nearby. 'As I watched,' he says, 'I realized it was being pushed out of the water by something underneath. This was the moment I'd been waiting for.' He grabbed his snorkel, mask and camera and plunged back in. 'I couldn't believe my luck when I discovered it wasn't just two but a stack of turtles mating.' They didn't appear bothered by Marcel's presence. Female green turtles may have multiple matings and produce eggs sired by different males, but they can also be choosy about whose sperm they use and are capable of storing sperm in their oviducts for long periods.