If you're an avid scuba diver or adventure junkie, you've probably heard of, or maybe even experienced the Great Blue Hole in the Belize Barrier Reef (an UNESCO World Heritage Site). Around 10,000 years ago, the hole's roof collapsed to reveal the previously concealed cave below. Measuring at around 1,000 feet in diameter (and around 412 feet deep), the cave sits in the Lighthouse Reef and it is close to a perfect circle.
At low tide, some of the reef (the white part in photos) actually protrudes from the water. The warm water and incredible visibility around the hole make the area great for beginner divers. If you're looking to dive the cave, go with a professional company to be safe (there are plenty of options).
Divers can expect the best views of underwater life at around 60 to 80 feet below the surface. Incredible stalactites that can measure as long as 130 feet, some of the largest parrot fish in the world, stingrays, and butterfly fish are just a few of the things you'll see while down there. Fun fact: Surprisingly, the hole is visible from space.