To be specific, he is a blackwater photographer. This is done in the open ocean. But to clear up any misunderstanding, it is not just diving into water at night. Blackwater diving is done where there is seemingly no bottom, in very deep water, using a downline and lights to attract sealife. The photographer is often looking for the unusual marine wildlife that's rarely, if ever, seen.

"The experience is amazing. Diving into the depths of the ocean makes me feel like I'm floating in infinite space with luminous marine creatures shining like stars," says Zhang, 35.

From the blue whale, the world's biggest mammal, and the rarely-seen blanket octopus to alien-like planktonic critters, the oceans are home to limitless life forms for Zhang to explore and record. He has been underwater in more than 30 countries and regions.