How do seals get their oxygen?

Seals can hold their breath for long periods of time, but they eventually need to surface to breathe air. They have several adaptations that allow them to stay underwater for so long.

* Large lungs: Seals have lungs that are about ten times larger than those of humans. This allows them to store more oxygen in their bodies.

* Slow heart rate: Seals' heart rates can slow down to as low as four beats per minute while they are underwater. This helps to conserve oxygen.

* Efficient circulation: Seals have a special circulatory system that allows them to deliver oxygen to their organs more efficiently.

* Counter-current heat exchange: Seals have a network of blood vessels in their flippers and tail that helps to transfer heat from their warm bodies to the cold water around them. This helps to keep them warm and conserve energy.

Seals are able to stay underwater for periods of up to two hours, but they typically only stay down for about ten minutes at a time. They surface to breathe quickly and then dive back down.