The ocean is home to the largest animals ever to have lived on Earth. Blue whales, reaching lengths of 30 meters and weights of 200 tonnes, feed almost exclusively on tiny krill. Whale sharks, the largest fish, can grow to 18 meters. Giant squid, with eyes the size of dinner plates, hunt in the deep ocean. These megafauna play critical roles in ocean ecosystems: whales alone contribute to nutrient cycling through their fecal plumes, stimulating phytoplankton growth and enhancing carbon sequestration.