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).
Blue Hole (Red Sea)
However, the Sinai Peninsula was occupied by Israel during the Six-Day War of 1967 (with Israel occupying the territory until 1982). The first people to dive the hole with modern scuba diving equipment were Israeli divers led by Alex Shell, who noticed the underwater arch in 1968. By the time Israel handed the Sinai Peninsula back to Egypt in 1982, the Blue Hole had developed a reputation as a diving site amongst the international scuba diving community.