The "Blue Economy" is used to describe all of the economic activities related to the sea, with a special emphasis on sustainability. Traditional activities such as fisheries, but also undersea mining, tourism, and scientific research are included, as well as the phenomenal growth of aquaculture during the past decade. All of these activities, and the irresistible prospect of another new frontier, has led to enthusiastic and, most likely, overenthusiastic assessments of the possibilities to exploit the sea to feed the world, provide low-cost energy, become a new source of minerals, and other future miracles. This book makes sense of these trends and of the future of the blue economy by following our remote ancestors who gradually discovered the sea and its resources, describing the so-called fisherman's curse - or why fishermen have always been poor, explaining why humans tend to destroy the resources on which we depend, and assessing the realistic expectations for extracting resources from the sea. Although the sea is not so badly overexploited as the land, our demands on ecosystem services are already above the oceans' sustainability limits. Some new ideas, including "fishing down" for untapped resources such as plankton, could lead to the collapse of the entire marine ecosystem.