Still relatively new in China, blackwater diving dates back to the early 1980s in Hawaii, the United States. Usually, blackwater photography involves hanging powerful light "baits" about every five meters down from a buoy, letting it drift in deep waters and waiting for the light to attract small marine creatures up from the depths to be photographed.

"It is a world full of surprises in which you never know what you will encounter," Zhang says.

With a true passion for the oceans, Zhang started blackwater photography in 2010 and hopes that one day he can publish a book as a field guide to life in the deep blue based on his images and descriptions.

"I have always been thinking about how to establish a database of different categories and how to make my text and images into an interesting book to help the public better understand the blue planet," Zhang says.