Marine biology gannets, and auks. Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland. There are five main types of marine mammals, namely cetaceans (toothed whales and baleen whales); sirenians such as manatees; pinnipeds including seals and the walrus; sea otters; and the polar bear. All are air-breathing, and while some such as the sperm whale can dive for prolonged periods, all must return to the surface to breathe. Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends
Toothed whale typically cruise at 5–15 knots, or ; the sperm whale, in comparison, can travel at speeds of up to . The fusing of the neck vertebrae, while increasing stability when swimming at high speeds, decreases flexibility, rendering them incapable of turning their heads; river dolphins, however, have unfused neck vertebrae and can turn their heads. When swimming, toothed whales rely on their tail fins to propel them through the water. Flipper movement is continuous. They swim by moving their tail fin and lower body up and down, propelling themselves through vertical movement, while their flippers are mainly used for steering.