Across the globe, scientists and civilians are noticing rapidly rising sea levels and higher tides pushing water into the places we live. By century's end, hundreds of millions of people may retreat from the world’s shores as coasts become inundated and landscapes transform. Jeff Goodell combines science and on-the-ground reporting from twelve countries to explain why sea level rise is happening, what it will mean for cities and island nations, and how societies are trying (and often failing) to adapt.