Seasteads - artificial settlements on the open sea - represent a near-future chance for multiple societal restarts. Where nation states suffer from ineffectiveness and inefficiency, both politically and economically, and cannot be changed due to path-dependency and rigidity, the open sea is a clean slate. Here, we can test new ways of doing things differently. This book discusses the opportunities and challenges of seasteads. Its focus is on socio-philosophical, political, economic, and legal aspects of founding new small societies of pro-active and productive individuals and groups. An explorative exercise, this book presents paradigmatic ideas and suggestions for partial aspects of seasteads.