The extent and diversity of Madang's marine environment is legendary amongst biologists, photographers and sport divers alike. The sheer volume of fish and coral life that engulfs the extensive barrier reef encircling the Madang area is unique - so unique that many species remain to be catalogued.

The walls of the reef are sheer and bottomless. The volcanic forces that spewed forth the northern coastline of PNG, aeons ago, have given rise to the ideal marine habitat. The deep waters of Astrolabe Bay surge along the walls of the barrier reef. The same fertile currents that gave birth to the Great Barrier Reef in Australia have shaped the evolution life in the seas off Madang. Being isolated from the rest of the Pacific, however, has ensured that its marine life has developed divergently from what one can experience anywhere else. More new species are being discovered along Madang's barrier reef than in any other marine site anywhere in the world. This has made it a popular research site for both the Cousteau Society and National Geographic.

The Barrier Reef is punctuated in three places by man-made and natural passages. These passages offer the best opportunity to experience the variety of Madang's fish life.