The water pressure around a human diver increases as he goes into deeper water. As the pressure increases, his blood is able to hold more dissolved oxygen. Our blood also absorbs the nitrogen in the air around us. If a diver were to move toward the surface too quickly, the nitrogen would start to bubble out of his blood. These bubbles can block the flow of blood to muscles, organs, and even the brain, leading to death. This painful condition is called the bends.

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