The blue economy covers a range of traditional and emerging sectors that are essential sources of food, energy, health and leisure for people throughout the world. The blue economy is growing fast and attracting investment worldwide. However, businesses often remain unsustainable. Illegal fishing, excessive tourism, polluting shipping and poorly designed port activities, are examples that threaten marine eco-systems and jeopardise the biodiversity that is essential to the prosperity of the planet. By 2030, one third of investments in the blue economy could be unsustainable ？ i.e., at least 250 billion euros invested in activities harmful to the oceans and ultimately the planet. Why is money flowing into damaging activities? This study found many reasons, including a focus on short-term profits, inadequate impact assessments, weak regulatory frameworks and businesses’ inability to attract impact investments. How can investments worldwide shift to activities that preserve the ocean and ensure long-term prosperity? While development banks are leading the change, they are unable to make significant changes alone. All financial players should be involved, including private equity funds, impact investors and policymakers. A sustainable blue economy is a global challenge that requires swift and coordinated global action. With this in mind, this report includes insights and recommendations for policymakers and investors.