Introduction to the Undersea Tunnel: The Undersea Tunnel is the most highlighted underwater landscape in the Phu Quoc Underwater World. Its length of 120 meters is the longest in Asia. Visitors can observe marine animals in all directions surrounded by sea water. In addition to a variety of sharks and rays, there are also dozens of large ocean fish, groups of coral reef fish, and more than 100 species of more than 2,000 unique marine animals such as the hawksbill turtle, a second-level national protected animal.