Two-thirds of our globe is Planet Ocean, not Planet Earth. Imagine a vast new source of sustainable and renewable energy that would also bring more equitable economies. A previously untapped source of farming that could produce significant new sources of nutrition. Future societies where people could choose the communities they want to live in, free from the restrictions of conventional citizenship. This bold vision of our near future as imagined in Seasteading attracted the powerful support of Silicon Valley’s Peter Thiel—and it may be drawing close to reality. Our planet is suffering from serious environmental problems: coastal flooding due to severe storms caused in part by atmospheric pollution and diminishing natural resources among them. But the seas can be home to a new breed of pioneers, seasteaders, who are willing to homestead the Blue Frontier. Oil platforms and cruise ships already inhabit the waters; now it’s time to take the next step to full-fledged ocean civilizations. Joe Quirk and Patri Friedman show us how cities built on floating platforms in the ocean will work, and they profile some of the visionaries who are implementing basic concepts of seasteading today. An entrepreneur’s dream, these floating cities will become laboratories for innovation and creativity. Seasteading may be visionary, but it already has begun proving the adage that yesterday’s science fiction is tomorrow’s science fact. Welcome to seavilization.