The term 'Giant Sea Mammal' can be summed up in one word: WHALE. Whales are the largest mammals in the ocean, and they are divided into two main groups: baleen whales and toothed whales. Baleen whales have a filter-feeding system, while toothed whales have teeth and feed on fish and other marine life. Whales are found in all oceans around the world, and some species can grow to be over 30 meters long.