The Great Blue Hole is a humongous underwater sinkhole that lies just 60 miles in the Caribbean Sea off the beautiful Belize coast. This hole, which, when seen from the top, is nearly a perfect circle and looks so inviting that it would be all you could to resist the temptation to jump in. Now, if Belize is breathtaking, the Great Blue Hole is a refreshing circle of dark indigo amidst all that turquoise water. The Great Blue Hole is part of the Lighthouse Reef System and sits just near its center. The 'hole' itself measures around 300 meters in diameter and 146 meters in depth.The Blue Hole was once a subterranean limestone cave system, but earthquakes and other geological events resulted in repeated collapses of the caves. So, what you now see is a 'blue hole'. You can still see the huge stalagmites and stalactites when you swim under the remains of the caves. The unique color of deep blue indigo is a result of the depth of the area. The Blue Hole is a National Monument and also a World Heritage Size. The Belize Audubon Society has assigned itself with the task of protecting this natural wonder. It is, however, to the world-renowned diver Jacques Cousteau that Belize owes much of its fame. His expeditions to the Blue Hole have brought it to the world's attention when he said that it is one of the top ten scuba diving sites in the world.The Blue Hole is surrounded by coral, home to anemones, gobies, and a collection of colorful fish and marine creatures – butterflyfish, hamlets, and angelfish (even some sharks!) well as purple sea fans and Elkhorn coral. The water inside the hole itself is motionless, and there is hardly any life here due to little light and poor circulation of the waters. However, as you dive deeper, you get to enjoy more spectacular sights as the water becomes clearer. When you reach the floor, the fine silt wafts up with your every movement. Exploring the hole is an adventure in itself, as this is really a gateway for a maze of passageways and caves. A tunnel leads to another tunnel and then on to another tunnel. Some even believe that some of the tunnels lead to the mainland. It is also a rare geographical phenomenon that many feel should be part of the world's famed natural wonders. Most experienced divers count this as part of their 'to-dive' list. And many of them will attest that the effort and the expense are well worth it.Be reminded, however, that due to the depth of the Blue Hole, only the experienced and the expert divers should delve into them. You will need all your diving skills to navigate the depths and the confusing maze correctly. If you still want to experience the Blue Hole, though, you can try the shallow diving opportunities afforded by the corals surrounding the hole. Of course, you should also be well aware of cave diving and safety rules.