As its name suggests, the Great Blue Hole is a marine sinkhole located near the coast of Belize. It’s 318 m across and 124 m deep. It’s known all over the globe as the ultimate scuba diving destination, but that’s not all. Thanks to its microclimate, scientists and marine creature experts have learned a great deal about what happens in the deepest waters of our planet. A guided tour of it can last for up to an entire day. Its name comes from the beautiful tonalities of blue created by the sudden change of depth in the water.