Oceans cover almost three-quarters of the Earth's surface and contain most of the planet's biodiversity. Yet for all their richness, the oceans are in deep trouble. Scientists estimate that up to ninety percent of the largest fish species have been lost over the past 50 years due to overfishing. Roughly two-thirds of the world's coral reefs are damaged or threatened, and about a quarter have been destroyed. Yet less than 1 percent of the world's oceans are highly protected in marine parks.