Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
Portsea Hole
The Portsea Hole in Port Phillip is about from the Portsea Pier. To the north there is a vertical wall approximately long. The wall has small overhangs which are home to plenty of marine life, including the beautiful Blue Devil fish. The Portsea Hole is a very popular boat dive site for recreational scuba diving activities.