A marine reserve is a designated area in the ocean where human activities are restricted to protect marine ecosystems and biodiversity. These areas are established to conserve fish populations, coral reefs, and other marine life, allowing them to thrive without the pressures of fishing, pollution, or habitat destruction. Marine reserves can vary in size and regulations, with some allowing limited fishing or recreational activities while others are fully protected. They play a crucial role in supporting sustainable fisheries and enhancing the resilience of marine environments against climate change and other threats.