When a whale dives, even though it fills its large lungs with oxygen, it cannot hold enough oxygen in its lungs with one breath to support a long dive. In addition to using the oxygen in its lungs, whales must also use oxygen stored in the blood and muscles. Whale muscle has high levels of myoglobin, a protein which draws oxygen from the blood, storing it in the muscle for use during a dive. Whales have a larger blood volume in relation to their body size than most animals and their blood is rich in hemoglobin which is used to carry oxygen all around the whale's body and to its brain. These two factors allow the whale to store up to 50 percent of its oxygen intake outside the lungs in the blood and muscles.
Some whales, particularly the [I 011 / sperm] whale, are very deep divers. They have been recorded diving over half a mile deep and staying under the water for up to an hour without taking a breath. [L3 105 / Whale's bodies are specially adapted to withstand very high water pressure].
