The ocean plays a vital role in sustaining life on Earth. It covers almost 75 percent of the globe and contains nearly a quarter of the world's known species—with many yet to be discovered. These waters sustain billions of people and myriad wildlife. But today, the ocean faces many threats, including industrial fishing, plastic waste, climate change, overfishing, and illegal fishing. Globally, almost 90 percent of fish stocks are fully exploited or overexploited, and about 1 in 5 fish is caught illegally. In the Pacific Ocean, bigeye tuna populations have been decimated. These trends must be reversed in order to protect marine biodiversity in these waters and to continue to sustain those who depend on them. A few healthy marine environments remain. They benefit from a great diversity of marine life that warrants conservation. The establishment of large and highly protected marine reserves would safeguard these sites and ensure their protection for the long term.