Covering more than 71% of the planet, the Earth's oceans are a vast and mostly unexplored mystery. For most of recorded history man could only guess what lay beneath the ocean's surface, but new technologies are reaching new depths. Researchers around the world are finding the unexpected - underwater complexes and sophisticated monuments that defy the conventional historical record. There remains of earth civilizations that were once exposed on land then later submerged under the sea due to climatic changes over 10,000 years ago. This implies that life on Earth - other advanced civilizations - once existed. They were lost to ice ages of the past that created great floods that destroyed them - which may be the fate of our planet in the future.