The term 'MASSIVE MARINE MAMMAL' can be summed up in one word: WHALE. Whales are the largest mammals in the ocean and are found in all of the world's oceans. They are highly intelligent and social animals, and they have been hunted for centuries for their meat, oil, and other products. Whales are an important part of the marine ecosystem, and their populations have been declining due to human activities such as overfishing and pollution.