2014, Turkey. A normal survey flight over Lake Iznik unexpectedly reveals the sunken remains a 4th century basilica. The discovery prompts scientists to probe the elusive history and geology behind the demise of the church that was built in ancient Nicaea -- now known as Iznik. When was the basilica destroyed? How did the basilica get swallowed up by Lake Iznik? And what happened to its community? Spanning the globe, this investigation follows a world-renowned team in this underwater excavation. Thanks to exclusive access to the site, including critical aerial and underwater cinematography, and spectacular CGI, we time travel through the centuries, back to the Roman and Byzantine time, and at the foundation of Christianity itself.