Graham Hancock discusses underwater archaeological discoveries suggesting advanced civilizations predating known history. Hancock examines submerged ruins off Japan, India, and elsewhere revealing sophisticated architecture beneath the ocean. The conversation explores Hancock's theory that rising sea levels at the end of the last ice age submerged coastal civilizations. Hancock discusses the Yonaguni monument and debate about whether structures represent natural formations or artificial construction. The discussion addresses resistance from mainstream archaeology to revising timelines and accepting evidence for advanced ancient cultures. Hancock examines connections between underwater sites and myths about lost civilizations including Atlantis. The broadcast explores what underwater archaeology reveals about human history and the limitations of current chronologies. Hancock discusses expeditions investigating submerged sites and the technical challenges of underwater archaeological work. The conversation addresses the implications of discovering sophisticated civilizations existing thousands of years before Sumer. Hancock examines evidence suggesting cataclysmic flooding destroyed advanced coastal cultures leaving only legends and submerged ruins.