The largest sea animal is the blue whale, which is also the heaviest animal on Earth. The blue whale weighs over 200 tons and can grow to 100 feet. Blue whales are magnificent marine mammals that have tongues as heavy as elephants and hearts as large as automobiles.
Blue whales grow to their enormous size on a diet that consists exclusively of small shrimp-like creatures known as krill. Depending on the season, an adult blue whale is capable of consuming more than 4 tons of krill daily. The baby blue whale enters the world as one of Earth’s largest creatures; blue whale calves are about 25 feet long and weigh close to 3 tons at birth.