Throughout the 20th century, the marine environment has been under attack, and the assailant has been us. Overfishing, pollution, habitat loss, biodiversity decline, ocean acidification, and an increase in marine heatwaves are challenging the living things that depend upon the ocean, including people. A sea change, however, is occurring in response to these troubling trends. More and more, humanity is revolutionizing its relationship with the ocean. For example, funding for marine conservation worldwide has doubled to nearly $2 billion over the last decade. Astonishing advances are being made in sustainable fishing, aquaculture, marine debris prevention and response, habitat restoration, offshore renewable energy, and ocean exploration and mapping.