Giant corporations are plundering the world's oceans, aided by global finance and complicit states, following the neoliberal maxim of Blue Growth. The situation is dire: rampant exploitation and corruption now drive all aspects of the ocean economy, destroying communities, intensifying inequalities, and driving fish populations and other ocean life towards extinction. This is an urgent call for change, from a campaigning economist responsible for some of the most innovative solutions to inequality of recent times. The oceans have been left out of calls for a Green New Deal but must be at the centre of the fight against climate change. How do we do it? By building a Blue Commons alternative: a transformative worldview and new set of proposals that prioritise the historic rights of local communities, the wellbeing of all people and, with it, the health of our oceans.