With more than 80% of our oceans still left unmapped and unexplored, there’s little doubt that many never-before-seen discoveries lie beneath the surface. The sheer power and breathtaking beauty of our oceans are undeniable, especially if you get a chance to glimpse these four amazing underwater formations – created by none other than Mother Nature herself.

Yonaguni Monument, Japan

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The ancient underwater pyramids rest mere meters beneath the waves off the coast of Yonaguni Jima, Japan’s southernmost island in the Okinawa Prefecture. Previously a popular shark-diving location, the architectural monument was only discovered in 1986 when the area was being scouted for hammerheads. Some people believe that this mighty monument is all that’s left of the legendary city of Mu, an ancient civilization rumored to have been swallowed by the sea roughly 2,000 years ago.

Others- like Professor Robert Schoch of Boston University – said he’s not convinced the monument was man-made. The science and mathematics expert attributes the sharp lines of the monument to the geology of sandstone rock and its tendency to break along a plane when located around tectonic plates. While no one can agree on how this far-out structure came to be, it gets our vote for one of the world’s most amazing underwater formations.

The Great Blue Hole, Belize

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Claiming the title of Belize’s top tourist destination, the Great Blue Hole houses one of the most diverse ecosystems in the world. At 300 meters across and 125 meters deep, it’s also the largest naturally-formed sinkhole of its kind. With stats like these, it’s no wonder divers come from every corner of the globe to dive the crystal-clear waters awash in marine life — of which only 10% has actually been discovered!

How did such a phenomenal hole form? It’s thought that the Blue Hole is a result of a multi-cave collapse during the Ice Age that was later filled in by the tropical Caribbean waters as the polar ice caps receded. It’s simply mind-boggling to think of all the elements that had to come together to produce this natural wonder making Belize’s Great Blue Hole nothing short of incredible.

Cenotes, Mexico

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You’d never know it from looking at the low-lying, relatively flat peninsula, void of surface rivers and streams, but Mexico’s east coast Yucatan Peninsula houses the two longest underground water systems in the world. Thanks to cenotes — natural sinkholes created when a cave ceiling collapses — you can explore these maze-like complexes via scuba diving.

Intrepid and properly-trained divers descend into the deep blue circular pool, surrounded by dense jungle, and soon discover a parallel universe existing just below the surface. The tunnels and caves that lie beneath formed thousands of years ago when acidic rainfall dissolved the porous limestone, collapsing the caves’ ceilings and creating a web of caverns adorned with columns of stalagmites and stalactites. This is a dive site designed for fearless scuba divers looking to push the limits of underwater exploration.