Fingal’s Cave, Inner Hebrides, Scotland. "Fingal's Cave is a sea cave on the uninhabited island of Staffa, in the Inner Hebrides of Scotland, part of a National Nature Reserve owned by the National Trust for Scotland" via Wikipedia.
The Great Blue Hole is the most popular dive destination in Belize. This massive hole under the water is near the Lighthouse Reef and creates a perfect circle of deep blue water. The water is 407 feet deep. It's breathtaking. YES BELIZE !