If you closed your eyes, spun a globe, and then randomly placed your finger on the map, where do you think you would land? Did you know that your finger would be much more likely to end up in the ocean than on land? That is because oceans cover more than twice as much of the Earth’s surface as land does. We, humans, need them: oceans and their diverse inhabitants provide us with food, water, fresh air, income, and recreation, and they even slow down human-made climate change. However, we do far too little to protect these gifts. We wanted to know how much ocean we must protect in order to safeguard its immense biodiversity and all the many valuable ecosystem services it provides. We found out that current protected areas cover far too little of the ocean. We need to set up many more protected areas to ensure the oceans’ and our own long-term well-being and sustainability.