Organizing for big data and open data, in our highly digitized world, is a necessity. Extant literature focuses on open collaboration in the context of business ecosystems and science. However, little attention has been paid to the kind of governance open data specifically requires, in a context of big data. We conduct a case study of the structuration of the oceanography ecosystem’s governance. Oceanography is an exemplar case of open and big data with an advanced governance of the ecosystem initiated more than 30 years ago. Our paper reveals a paradox, namely that efficient open data needs highly structured coalitional governance. This governance involves three coordination mechanisms: data foundation (by actors that produce the data), global piloting (of public and private actors’ interests), and implementation (of open data platforms with their extension markets).