Great Blue Hole is an amazing masterpiece. It is the largest ocean basin in the form of a shell. Within the walls of the pit is a huge cave with the incredible size of the limestone pillars (up to 10 meters). Underwater lights are mandatory part of the equipment when its diving in those places. It is assumed that thousands of years ago, Big Blue Hole was an ordinary cave, which was collapsed under the impact of the water, advancing to the mainland. Thus was formed a funnel filled with water depth of 124 meters and a width of 300 meters. This hole came to be known by the French explorer Jacques Yves Cousteau, who included it in to the top 10 places in the world for diving. In 1972, on his vessel Calypso, he measured the depth of the hole and confirmed the theory of its formation.