Sperm whale

Sperm whales have ribs that flex after greater water pressure, which allows them to dive deep.

An excerpt from the article 20 facts about sperm whale

When diving, they keep their metabolism to a minimum and supply blood only to their most important organs: the heart, brain, and spinal cord. They can store a large amount of oxygen in their blood and muscles.

Sperm whales’ blook has 50 percent higher hemoglobin content than that of humans.