Hidden behind the dense curtain of the ocean water and singing an eerie song of their own, whales are the gentle giants of the deepest depths. Whales are built similarly to the Hippopotamus and are warm-blooded with a layer of blubber to help insulate and moderate body temperature. Large flippers allow them to navigate the ocean currents, and their blowholes on the top of their head allow a quick breath before diving again. Some whales can hold their breath for up to 90 minutes.