The largest mammal in the ocean is the blue whale (*Balaenoptera musculus*). These magnificent creatures can reach lengths of up to 100 feet (30 meters) and weigh as much as 200 tons or more, making them the largest animals ever known to have existed on Earth. Blue whales are filter feeders, primarily consuming tiny shrimp-like animals called krill. They play a crucial role in marine ecosystems and are known for their deep, resonating calls, which can travel long distances underwater. Despite their immense size, blue whales are gentle giants.