The marine life in these areas includes nurse sharks, giant groupers, and several types of reef sharks such as the Caribbean reef shark and the Blacktip shark. Dive excursions to the Great Blue Hole are full-day trips, that usually consist of one dive in the Blue Hole and two additional dives in nearby reefs. The Great Blue Hole is in our list of Top 10 Reasons Why You Should Visit Belize. The Great Blue Hole is a large underwater sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll 100 kilometres (62 mi) from the mainland of Belize City.