The Great Barrier Reef is the largest coral reef system in the world and is located off the coast of Cairns, Australia. It is a UNESCO World Heritage Site and is home to a variety of marine life, including over 1,500 species of fish. Visitors can explore the Great Barrier Reef in a variety of ways, including snorkeling, scuba diving, glass-bottom boat tours and helicopter flights. Tours can be arranged from Cairns, Port Douglas or nearby islands. It is important to choose a tour operator that practices responsible tourism to protect the reef's fragile ecosystem.