Recent sharp declines in numerous fish species and other ocean wildlife have forced serious reevaluation of old assumptions about the capacity of marine systems to sustain large-scale taking, especially when coupled with drastic habitat destruction, by-catch and food-web disruptions. Achieving ‘sustainable use’ of ocean wildlife is a widely-held goal, but present capacity to find, extract and transport marine life to distant markets generally exceeds the capacity of the exploited species and supporting ecosystems to recover. The role of fully protected areas within large marine management regimes or ‘seascapes’ is becoming recognised as a vital part of what is needed to restore depleted populations and ecosystems and maintain their long-term integrity. Already, some nations have begun to develop broad management plans for their Exclusive Economic Zones and to consider policies governing protection and use of wildlife in the 60% of the ocean beyond national jurisdictions. Protection of breeding, feeding and nursery areas, more realistic catch expectations and development of non-destructive methods of extraction will help reverse the present declines. But inevitably, maintaining or enhancing present levels of food derived from aquatic animals will depend on identifying and cultivating the ocean and freshwater equivalents of cows, chickens and pigs — fast growing, nutritious creatures that are low on the food chain. These issues are explored in this paper, together with a focus on the economic and ecological importance of marine life other than as marketable commodities. In particular, the importance of life in the ocean as essential components of Earth’s ‘life support system’ is acknowledged and a case made for maintaining the health of the ocean as a fundamental requirement for enduring human security.