The document is about marine mammals like dolphins and whales. It describes their physical characteristics such as being gray, big bodied with two flippers, a fin, long nose, and tail. It mentions that they swim very fast, jump, leap, play with people, catch fish, and communicate with each other. Specific details provided include that blue whales are the largest animal to ever live, can be heard from hundreds of kilometers away, breathe through a blowhole, and are endangered with only about 10,000 remaining. Killer whales are also discussed as being large dolphins with teeth that can swim 50 km/hr and are important for tourism.