The largest mammal found in the ocean is the blue whale (Balaenoptera musculus). These magnificent creatures can grow up to 100 feet long and weigh as much as 200 tons, making them the largest animal known to have ever existed on Earth. Blue whales are filter feeders, primarily subsisting on small shrimp-like animals called krill. They are known for their incredible vocalizations, which can travel long distances underwater. Despite their immense size, blue whales were once hunted extensively, leading to a significant decline in their population. Conservation efforts are ongoing to protect this iconic species and its habitats.