Privatization of the ocean, in the sense of defining more exclusive property rights, is taking place in increasingly diverse ways. Because of more intensive and diversified use patterns and increasing sustainability challenges, it is likely that this process will continue into the future. We argue that the nature of privatization varies from one oceanic domain to another. We differentiate four ideal-typical domains: (1) resources, (2) space, (3) governance control, and (4) knowledge, and nine criteria for the assessment of privatization. We apply those criteria to a selection of examples from the realm of marine life (from micro-organisms to fish) to highlight similarities and differences and establish foundations for broader analysis. We aim hereby to develop the groundwork for a balanced, interdisciplinary perspective on ocean privatization. Our analysis demonstrates that privatization has multiple dimensions and cannot be condemned or embraced in its entirety. Instead it requires more nuanced assessment and deliberation.